I had been using a £6 Ikea 14" TV wall bracket to mount my Panny PT-AE100 on the back wall. I'd been using the bracket the usual way up and as a result had -12 keystone (projector is desk mode). Not good, so I have decided to turn the bracket upside down and suspend the projector underneath. I just need to drill 4 holes and attach the projector using screws. Anyone know what size screws I should get????