Fred: there's a difference between sugarcoating and civility. You do not need to do the former, but the latter is usually appreciated, and goes a long way towards getting your point across better and with less hostility. Nobody is doubting your knowledge, just the way that you are attempting to communicate it.
As for the new sims, I would still advise a test flight (ideally, a supersonic one) prior to the M750 flight. If you can spare the $250 or so, a CTI L2375 White Thunder or an AT L2200 Mojave Green would be great to get your rocket supersonic, and would also be a good test of the rocket itself to ensure it performs as expected. I have flown both of those motors in my 4" AMRAAM to over 0.90 mach and over 11,000 feet, and it weighs more than twice as much as your rocket. Therefore, I would bet that yours would attain over 15k and well over mach on either motor, and you would get excellent performance data to ensure that your simulations are at least reasonably accurate. Other rockets' data is nice, but there is quite a bit of variation from fairly subtle effects that is hard to truly account for without data from your specific rocket. One local club member that I know (who is incredible with altitude rockets - he recently attained 16,379 on an I600R) has some data on nose cones showing a fairly significant variation in the supersonic Cd with fairly subtle changes in nose shape.
Finish also makes a huge difference - my Cirrus Dart went 11,950 on an I600R, while m85476585's went around 8400 feet. The difference was a few ounces, a couple rail buttons, and (perhaps most importantly) that mine had an auto paint finish while his was only partially painted with spray paint. When you're talking about going this high and fast, subtle changes make a surprising difference, which is why I would still be somewhat reluctant to sign off on your flight if I were the RSO if you didn't have any data on your specific rocket (although there are some exceptions - if the 26000 foot flight was on a rocket that was provably significantly more optimum than yours, with a better finish and a more optimized nose cone, I might allow it).