fuel tank screws removal

I've got most of the parts in hand to rollerize my new 09 GRiSO, but hit a snag already removing the fuel tank, even before I get to the not too quick release. The two rear screws fasten into a rubber bushing of some sort, but after turning more than a quarter turn's worth of elasticity, they're not breaking loose. I don't remember this being a problem on my last GRiSO. Is there a risk of breaking something, particularly the fuel tank, if I torque them further till they just break loose?
Doug

They will either break loose or tear. If they tear you then have to get the threaded bit out of the frame and then buy new ones.

Thanks Pete. With a little more force the screws and rubbers came out together from the frame. It wasn't too hard to separate them from the tank after that. Fuel tank is now off via the injectors and next step is deflate the tensioner.
Doug

Glad you got them out. When I have bolts stuck, I put a socket over the bolt head, or in this case an allen socket and whack it carefully with a hammer to break the threads loose. Helps 90% of the time.

Thanks Bulldog. As much as. I like judicious hammer application, these were screwed into a sort of rubber sleeve bushing so they move with the elastic. The hammer just bounces back in your face .Doug