livingston,
If you have verified the 12.5" meter pressure to be stable, then fluctuating flame is probably due to residual air and / or water vapor mixed in the incoming propane. You mention having new orifices installed. A new installation of piping or storage tank will have air in the piping or tank, and possibly some residual water from the tank hydrotest. The propane supplier will need to help you, if the problem is purging the storage tank, but you could purge the piping yourself if carefully venting the end of line flow, avoiding any open flame in vicinity, and waiting for propane to disperse before attempting to re-light pilot flame or burners. If it is air in the piping, then you might already have had suffucient flow to purge out the air by now.
Fisher Controls-Regulators LP-Gas Division has booklet LP-10 LP-Gas Serviceman's handbook with pages 15-17 data and info for preparing and purging containers. REGO also has their LP-Gas Servicemans manual, pg 8-11 with data and info for preparing and purging containers.
The Fisher Controls LP-Gas webpages can be reached through
, selecting 'Products', then 'LP-Gas Equipment', 'technical references', LP-10 handbook.
The REGO - Engineered Controls Int'l webpages can be reached at
, select 'LP-Gas Service Manual'