We are having a problem with our bedroom slide on our 2006 KZ Escalade. When the slide is closed, it is down about 1/4" on the outside. We took it into the local RV shop and they said the problem is...
I doubt that a sheet of aluminum would be strong enough in itself to shore it up. If it cracked, the support structure of the floor is inadequate. Also as you said, it must be smooth where the rollers travel over for it to work right.