First off appologies for going down a cealry well trodden path again but I am hoping for some advice on thicknesses of plasterboard to use for a wall. For preference I would like to use 12.5mm, however I have checked and this will leave barely 1mm for a skim around door linings. (if that even, basically the 12.5mm board will be pretty much flush with the linings) I am concerened that this is not sufficient for the plaster skim and am curious whether 9.5 mm boards can be used here. Stud is vertical only 4x2s at 18inch centres. (approx 450mm centres for metric people, but i'm sure you all know that ) Making gap between boards roughly 14 inches (350mm). Will 9.5mm board be rigid enough here or shoud I use the 12.5mm?