Thor Chateau V25 on E350 chassis. I know this won't help your situation now, but I had the same problem.
After bottoming out numerous times, I decided to put on rolling swivel wheels. See left pic. But within a few scrapes they shattered. Maybe they made out of pot metal and just could handle the weight and impact. Obviously, they didn't work.
I came up with a custom solution. A 2.5" steel pipe installed on a 1.5" steel bar welded to the frame. See right pic. Photo is terrible, but imagine an empty toilet paper roll sitting on a TP holder. I had it set low enough to clear the jacks. I still bottom out every once in a while and it sounds horrible, but I feel confident that I'm not going to do any damage to the underside and parts.
Jeff & Naomi & Ryu
2019 Thor Chateau V25 Class C SKP: 154598, Good Sam: 813449980
Upgrades: 190W Go Power Overlander Solar Panel, EPever 40A Tracer MPPT Controller, Xantrex Freedom XC 2000W 80A Inverter/Charger, 4x6v VMAX AGM 240Ah Battery Bank, SeeLevel III Tank Monitor, Big Foot Leveling Jacks, Jensen CAR1000