I need to stud mount a hdu sign to a block wall. The sign will be about 48" square and 1" thick. It needs to stand off the wall about 1.5". I'm planning using at least 18lb hdu but I'm still concerned about the studs ripping out of the hdu. I could put a piece of dibond on the back and I think that would help but I'm not sure its enough. Any suggestions for doing this? The sign will be about 15' in the air so I need to know for sure it isnt falling down.