Just use caution when you intentionally go outside the book, and take real good notes to share the facts with us upon successful completion of your flight test.
Well Dan, we that fly 150/150's, and 150/180's, are all test pilots by your definition. For our aircraft came to us with neither a pertinent owner's manual, nor any performance information.
But, I believe that you mean well, so, what exactly would you like to know from my notes? Actually, most of my experiences I have already posted here on previous occasions, haven't I?
If I take off over weight will my insurance cover me?..............
Probably not.
I have asked this many times before, but I will ask it again since you have raised the issue, Dan:
AHEM...........
How many people here have any first hand personal knowledge of having an insurance claim being denied strictly due to being over gross?
What about Va ? As we increase the weight of the aircraft the Va speed goes up, we can over stress things that way also.
AHEM.........Wouldn't that translate to LESS likelihood of over stressing the airplane, Dan? I mean, doesn't that mean that the heavier the airplane, the higher the airspeed required to do structural damage??

Thanks for the use of your soap box, Dan!

Next??