There is a graph on RVP as function of % ethanol (0-100%) in the blend that may be of interest, in the following site:

www.deh.gov.au/atmosphere/fuelquality/publications/review-non-automotive/operability-1.html

Putting your question into Google results in a link http://www.baylor.edu/bias/index.php?id=4556 . This states that denatured ethanol has an RVP of 3. I can't comment on your "up to 5% gasoline" other than that I thought 1% was used.

HAZOP at www.curryhydrocarbons.ca

The 5% comes from the ethanol for fuel blending specifications.  I believe that the actual spec is 2.5 to 5% however I am assuming that it would be advantageous to add as much gasoline to the ethanol as possible to help with the economics:  Ethanol being considerably more $ than gas.

Thanks for the information!!

The link I mentioned above uses a gasoline of RVP = 9 (≈ 62 kPa). Since 1 psi = 6.895 kPa.

Here's some notes I recently made while making a quick and dirty study on ethanol pipelines,
********************************************************
Seems like the biggest complaint is corrosion potential.  It also seems that it is a very controversial topic.  
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Buckeye Pipeline did tests in the 90s from New Haven to Springfield Ma
ethanol batches got cleaner with more being shipped
cleaned the pipeline of water deposits
should be shipped between reg nolead gasoline and premium nolead gasoline.
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Amoco Tests
Higher concentration ethanol blends resisted separation for longer periods
Blends were more likely to separate with colder temperatures

****************************************************************************************
                             Potential problem areas,
**************************************************************************************

Corrosion (Maybe this reason is being used as a reason to squash pipeline shippment feasibility)
Water pickup from low areas in the pipeline
Sulfur pickup from pipeline wall deposits
Higher vapor pressure (gives a 1 psi lower NPSHA)
Discoloration
Making gums
Handling of interfacial mixtures generated with the leading and trailing products
Closed tanks needed to prevent rainwater leaking in from a floating roof.
Quality control programs
Safety procedures and training
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"As is done in Brazil, neat ethanol shpment by commercial pipeline is seen to be viable in the Archer Daniels Midland-Williams Pipeline tests and observations."

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Petrobras is thinking about building a BIG one.
http://biopact.com/2006/04/brazil-planning-500-million-ethanol.html
http://www.greencarcongress.com/2006/02/petrobras_consi.html
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http://www.us-dev.com/news.htm

Even though the sweet vodka-like smell of a tank car usually leaves little doubt it holds ethanol, Lomita's efficient six-person crew must sample the temperature, density, and clarity of each car before it's drained into a manifold running into a 4-mile ethanol pipeline. "This whole process is costly," says terminal manager Tim Lewallen, "but it's very little compared to contaminating a whole tank." There is always a remote chance a car could contain something else.

Next stop for ethanol from KAAPA and other Midwest producers is the Shell Oil Products U.S. 480-acre tank farm in Carson at the other end of the new pipeline. There, Shell has refurbished five 65,000-barrel storage tanks to hold ethanol. Those and other improvements made to switch from MTBE to ethanol cost the company $35 million. From there, 100 fuel trucks a day haul ethanol to blenders that supply gasoline to most of the major oil companies in the southern California market.

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SEMCO PIPELINE CO has recently filed for a permit to build an ethanol pipeline in Michigan.
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"Because ethanol can be corrosive to some metals and damaging to rubbers (gaskets and seals), fuel-storage tanks and dispensing equipment must be corrosion and damage resistant."
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http://age-web.age.uiuc.edu/faculty/qzhang/Publications/2005BT96(2)Hansen.pdf

"General corrosion was caused by ionic
impurities, mainly chloride ions and acetic acid. Dry
corrosion was attributed to the ethanol molecule and its
polarity. de la Harpe (1988) reviewed reports of dry
corrosion of metals by ethanol and found that magnesium,
lead and aluminum were susceptible to chemical
attack by dry ethanol.
Wet corrosion is caused by azeotropic water, which
oxidizes most metals (Brink et al., 1986). Freshly formulated
blends containing pH neutral dry ethanol
would be expected to have relatively little corrosive effect.
However, if a blend has been standing in a tank for
sufficient time to allow the ethanol to absorb moisture
from the atmosphere, it may tend to be more corrosive
as it passes through the fuel injection system (de la
Harpe, 1988). In addition, the fuel may stand in the fuel
injection pump for a number of months, for example in
a combine harvester engine, thus allowing the fuel time
to corrode parts of the pump internally. Corrosion
inhibitors have been incorporated in some additive
packages used with ethanol–diesel blends (de la Harpe,
1988).
Non-metallic components have also been affected by
ethanol with particular reference to elastomeric components
such as seals and O-rings in the fuel injection
system. These seals tend to swell and stiffen. Resinbonded
or resin-sealed components also are susceptible
to swelling and seals may be compromised (Bosch,
2001)."
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http://www.deq.state.or.us/wmc/pubs/factsheets/tank/FuelEthanolUSTSystems.pdf

Is Fuel Ethanol Compatible with Current Underground Storage Tank Systems?
In most cases the simple answer is probably not. Unlike petroleum-based fuels, ethanol conducts electricity. As such, it is much more aggressive in dissolving soft metals such as aluminum, brass, zinc and lead. Once dissolved, these metals may be deposited in engines following combustion and can lead to fouling and poor engine performance. Unplated steel, stainless steel, black iron and bronze have shown acceptable resistance to ethanol corrosion. Fuel ethanol may also cause rapid deterioration of some early generation (prior to 1992) plastics, fiberglass, cork gaskets, natural rubber and leather, among other materials. Some nonmetallic materials that have been successfully used with ethanol include thermoset reinforced fiberglass, Neoprene rubber, polypropylene, nitrile and Teflon, among others.
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                  Conventional  Gasohol MTBE   Reformulated
                    gasoline      10%   Blend  Gasoline

Vapor Pressure: Summer 8.7        9.7    8.7    7.2
Vapor Pressure: Winter 11.5      11.5   11.5   11.5
Benzene(vol%)          1.6        1.6    1.6    1.0
Sulfur (ppm)           338        305    313    302
MTBE(vol%)*             -         -      15     11
Ethanol(vol%)*          -         10     7.7    5.7

BigInch-born in the trenches.
http://virtualpipeline.spaces.msn.com

Thanks BigInch!!

Lots of information there.  As a company policy (so far) we will not accept gasoline with ethanol in it.  We do not have a retail distribution system and only move gasoline in and out by marine and pipeline.  
Ethanol storage is limited to dedicated systems storing ethanol denatured up to 5% gasoline.  Tank specs are as follows.  Welded floors and shells with a minimum of the welds being lined (6" on either side) on the floor and one course up the shell.  IFRs are typically aluminum pontoons, stainless mechnical shoe primary with a teflon vapor barrier and secondary compression plate mounted on the rim or PVC/nitrile wiper secondary, depending on the tank diameter.  The PVC/nitrile wipers are very stiff and not recommended for tanks with a diameter less than 60' or so.