Your avatar picture shows a motorhome, but you posted in the trailers and fifth wheels section, so I'll assume that you have a trailer of some sort. Almost every trailer manufacturer I've ever seen recommends AGAINST using any kind of support under a slide room. I can't speak for motorhomes, as I've never owned one, but would think that they are pretty much the same thing. The reason being is that if the trailer settles for some reason, like heavy rains or ????, if the slide is supported and does not settle along with the trailer, there could be significant damage to the slides. My owner's manual for my Grand Design Momentum specifically states to NEVER use any type of support under a slide room.