RV manufacturers warn NOT to use them, as it will void the warranty if you have any slideout problems.
Slideout supports are leftovers from the early days of slideouts when the technology was new and there were issues.
Modern slideouts shouldn't need them.
That's why you don't see them being used.
Dan-Retired California Firefighter/EMT
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package