You've probably already confirmed this, but I would mention that you must get the rear hatch closed securely on BOTH sides, or it will do exactly what you're describing.
When I first got my GT I feared I'd need a friend to ensure I got it closed right everytime I opened it (one guy on each side, pushing down simultaneously). But then I learned that if you place your hand in the exact middle of the rear engine cover (right on the stripe, if you've got one) and then push with strong, firm (but not necessarily "slamming") force it will latch securely on both sides every time.
I did notice a weird soreness in my elbow after a few days of GT ownership back in August 2005, but then I realized, "You know, that closing technique probaby puts some healthy force on my joint that it's never experienced before, considering how far out I have to extend my arm to get to the center of the shell, and then how hard I have to push down."
But like my entry/exit technique in my tight garage space, my body quickly trained itself to execute this move without any residual effeects. :wink
Maybe we should put a list together of the specific muscle groups we've all strengthened by owning a GT. :lol