Trying to remove the screen from my '94 TA to fit the low one I just treated myself to but can't shift any of the 4 fixing screws, the whole thing just turns. Even where I can get grips to the back of a couple of them they won't undo. 2 on the left side front body panel are also stuck firm. Have sprayed with PlusGas but no joy yet. Is there a good answer? Drill them out?