Hi, I have a 2015 Elddis built motorhome. The habitation door is only single point locking in the centre. I have sourced some Fiamma safe door Guardian deadlocks, the catalogue number is 29534. They simply fit on the inside of the door with 3 screws. I am concerned regarding putting self tapping screws into the inside of the door. I don't actually know what the material is, it's GRP on the outside clearly I wouldn't use anything more than 12mm in length. I have toyed with the idea of fixing a plastic doubler, say 3mm with one of the high bond adhesives then some adhesive behind the lock and then the screws. I realise fitting them top and bottom will only make the door about 30% stronger with regard to a burglary but it's better than nothing, in my opinion. Any bright ideas are welcome.