Camper jacks on large casters

I've got a set of casters with 8" diam solid rubber wheels that can be bolted onto the footpads of the Happijacs on my Outfitter Apex. They work fine in the garage where the concrete is smooth. I can push the camper to the back by myself, and when ready to load, back the truck close and push the camper into alignment. The two front Happijacs DID splay outwards, so I installed a stainless steel rod across to tie them together. But my driveway up to the garage is sloped, which is a huge pain particularly when trying to load the camper, so I haven't used the wheels recently for that reason.