Before I called it a day tonight I used the screws in the boards and assumed they where the stud wall.....too thin for the clug screws. Can get one in the stud and the other misses. Maximum depth is 40mm before hitting vapour barrier. Found some Rawplugs used for cavities and hollow doors that think will do the trick. It’s only holding a MTB after allfind the wooden studs & drill into them. sometimes ppl will mount a board to the wall using the studs, then mount stuff to that board