We have a 2007 Springdale 290CT with a 13' slide that has about 1/2" of sag in the middle. I talked to a local rv repair shop and they said their repair would be to remove the trim on the inside, jack...
My main concern is to make sure the slide seals and right now the middle of the seal just touches. I like the idea of a support in the middle but the way my slide tips up when it closes I don't think it would work right.