Hi - I was going to stick some insulated plasterboard in my garage but one wall is a bit tricky - the timber that the joists are resting on at the top of the wall is sticking out by about half an inch. I'm wondering if I can blob the adhesive on to half an inch thickness so that the board will sit flush with that timber and be half an inch off the block wall lower down? Or...should I put half inch battens on the wall and screw the boards to that? Will half an inch be enough for the drywall screws to bite on? The boards would be about 40mm thick in total, so if I got 50mm screws that should work, in theory... Thanks!