Modern slide-outs are not designed for supports. If your trailer settles, jacks under the slide-out will bend or break the moving mechanism in a best case scenario. There are jacks sold that have a collapsible feature, so when your trailer settles the jacks collapse to prevent slide-out damage. I think you are asking for trouble using jacks.
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired, Good Sam Life member.
The Constitution is not neutral. It was designed to take the government off the backs of people. Supreme Court Justice Douglas