When I was getting scheduled maintenance on my auto transmission, the guy at AAMCO---knew of a technical service bulletin ( TSB's ) for my 05 V6. Same problem as yours "harsh reverse engagement" lucky I was still under warranty and my ford dealer changed some solenoids and other parts to fix the problem.
Suggest you check out the TSB section for more info.
Mods : Flowmaster 40s Dual Exhaust--H-pipe
"Life is not always fair but it's always good... behind the wheel of America's Sports car, the Mustang."