Trailer had some crappy 4 stud 13" wheels on it, so that was never going to fly. I picked up a set of new 5 stud 4.5" (Ford) pattern hubs, then used some G2 adapter/spacers designed to allow TJ's to use JK wheels....ie, 4.5" PCD to 5" PCD. The spacers took up the extra offset of the JK wheels perfectly, and also spaced the wheel away from the hub bearings which would otherwise stop you from using JK wheels (or make you machine out the JK wheels and thereby making them useless on the Jeep).
I wouldn't use spacers on anything with a lot of weight in it, but this is a small box trailer that'll only be carrying a bit of camping gear.....can't see it'll be a problem.