43,000 lbst is a lot to play with in the subsonic regime. But the combined effects of stuffing a 4500 lb capacity weapon bay into the midriff, ramming a THING the same diameter as a regional jet's engine into a hole behind the cockpit, and keeping the beast short enough to fit on an elevator that was designed in the 1960s for helicopters, sort of catch up with you as you pass 0.9.