Hi all, need some extra advice here. Just bought a stone resin shower tray and Im fitting it onto 18mm marine ply that has been sealed with PVA. I spoke to the manufacturers about bedding it in. I believe a lot of people use some kind of mastic although it will void the warranty. I've been told to use a weak sand/cement mix 5:1 and its to be semi dry. I'm worried if it's to wet it may damage the hardboard, am I worrying too much? Also the instructions speak of anti crumble additive, again I've been told to use PVA or washing up liquid, what do you thnk? cheers in advance.