I don't know how anyone else sets up. All my corner jacks go on 2x6's and checked often. The corner jacks are on the frame and the slide is not dependent on the tires but are on the frame. The slide out would work fine without tires or axles even on it if the frame was supported properly!
Would I use slide supports with the phony electric stabilizers.. No.. But I do with the scissors jacks on solid ground.
A flat tire cannot effect the slide at all if the trailer frame is properly blocked up/secured....
This is Idaho and we live on solid ground.:B