Changing dimensions will not change the solid object. Also, unless it's new since 2004, you cannot stretch a solid. You must offset the face + or - the amount you wish to change it.
I have used the teflon spacers in various applications in chemical process. Look up Crane Resistoflex and they can help you with the specifics. They specialize in lined pipe, but offer a wide range of spacers also.
If you decide to go with the steel blind flange spacer, it would be the same as...
The back side of the blind flange is not suitable as a gasket surface, however, any machine shop should be able to put a gasket surface finish on it for you. Depending on the service, and temperature, you could also just purchase a teflon FF spacer which also serves as the gasket.
Guess I can add an un-educated 2 cents worth. As a pipefitter we were told the 45 degree cut was simply to minimize the whistling when discharging. As a designer, I've never asked why, and have never been told not too.
As others have stated, there are standards which you will find in pipefitter handbooks such as W.V Graves Pipefitters Blue Book and Thomas W. Franklands The Pipe Fitters and Pipe Welders Handbook. However, little things like the setting of the cut depth on the threading machine can cause this to...
