I like using all swivel casters because I parallel park my camper in a tight space in my barn. It's almost impossible to do this with fixed casters, especially when you're positioning the camper by hand. I didn't mount a tow bar and there's no room for a tractor where I park the camper. When I need to move in a direction greatly different from the way the casters are pointed, I just use the camper jacks to take a load off the dolly, re-position the casters by hand, raise the jacks and roll. Another advantage to all swivel casters is that as many as necessary can be used. eBay has a set of four 1000# casters for about $45. Eight of these would cost less than four of the $37 swivel casters mentioned above and carry significantly more load.