The longer the rod the further the front edge of the top on that side will end up farther forward. After you reach a certain (overall) length of the front pushrod, it will start to retract just as it reaches its final position (
i.e., when the electric motor cuts off and the idiot light on the dash goes out).
You can't mess anything up that would damage the top with these adjustments, and you should increase the length of the pushrod very gradually to see what results you get.
I think that having the front edge of the top end up further forward might mean that the front edge might lift upwards a little higher when it first starts moving, perhaps enough to alleviate that pulling on the gasket.
Also double check that your tension ropes are intact and attached. Those are located underneath the rear main bow of the convertible top frame, the ones that you "unsnap" when putting the top in the service position. Those serve to keep the rear main bow pulled down and that create pulling tension on the convertible top canvas.
Regards, Maurice.