I also used stranded copper running through light weight water tight conduit available from Home Depot (Home Depot, Camping World, etc is where I got the vast majority of my supplies-of which there are many stores nationwide).
I just recently had to replace one of my main 50amp breakers. They were two separate breakers that I replaced with one double 50 for the generator. The old one kept tripping, so I thought it was worn out since it is used for the gen/land hook up. When I took it apart, the screw holding the wire was not very tight. May have been the problem, but still replaced it. With our mobile homes vibrating down the road, we should have a scheduled program to tighten accessible connections routinely to prevent problems. Good Luck, TomC