Hammer,
I've generally run 3 tests, the light, medium, and heavyweight on each aircraft. I consider this a method to give best/worst numbers and then the medium is what I'd consider "typical" but depends on aircraft in question, usually around 3/4 internal with no external ord and what I'd consider the most "common" gun package you would likely meet.
That way, you can plan for the worst and do some extrapolation of where you think you are in relation to the numbers I've tested. The differences can be pretty dramatic.
Whatcha planning to test, btw? I'm working on a bunch of tests for the AH aircraft right now.
-Soda