Big-Foot-
My car is a GT premium with the power seat and a manual tranny. I put my seat all the way back, all the way down in the back, but I raise the front up just a bit. Works out fine. I don't need any added length on the rails.
I'm 6'7", 240 with a 36" inseam and i fit just nicely in my GT. My shins don't rub on the bottom of the dash but my right knee rests against the console. I'm not going to reposition my seat.