Just picked up a wee job that has been first fixed. The finished walls are made up of something like 6 or 8mm ply. We usually use Appleby fast fix boxes but I tested one and they won't tighten up due to the thinness of the ply. I was wondering if there was a dry lining box available that would do the job? (ie. less space between front of box and lug). Trying to avoid metal boxes as nothing has been dwanged!