Hey I have installed a lightweight foam shower tray as per manufactures instructions on a bed of sand and cement 5.1. However it hasn't stuck very good at the front of the tray there in a bit of bounce. This is the second time iv installed and had problems with foam trays. Never had a problem with stone resin ones. I even put weight on the tray till it set. Any one else had problems with these trays? I'm thinking of scraping some of the mortar out at the front of the tray and squirting expanding foam in.