Gerald,
I was reading the Slide Alignment thread from back in Feb where you advised sleeving the slide rollers with sch 40 PVC. My front slide sagged in the back. BCS suggested that I check for floor compression above the rollers, which is what I found. As a fix, I inserted 3/16" steel plates for the rollers to run on for the 2 rear sets of rollers. This made a big improvement but it still isn't perfectly level.
I used 2 farm jacks to raise the slide as much as possible and would have installed a 1/4" plate but couldn't get the clearance needed. My rollers are metal with no covering. The addition of PVC sleeves would probably level the slide but its not clear to me how one gets the rollers out w/o lifting the slide even more.
Thx, Steve