On my grandby I get it close and then take the jacks off, then I physically lift and push it where I want it to go. I don't have a bedliner and it doesn't take all that much to move it an1-2 inches here or there. It slides much easier then you would think. At least it does for me.
1990 Ford F-250
1997 fwc grandby
1990 Ford F-250
1997 fwc grandby