5th wheel with Class III hitch on back - Excel - who else?

I think I would be concerned towing anything 4 down behind a 5er or TT. That would put a lot of strain on the frame during turns. On a trailer or dolly would seem to lessen the strain a bit. I've often thought one of the new Fiats or Smart Car would be handy when Snow Birding, but just not sure the advantage would out weigh the possible issues.