our team doesn't have a trailer(yet
) but my youth group has a nice 5X8 that pulls nice with everything i have used(have not try the minivan just 15 and 12 passenger vans i don't know what brand it is... i can look when i am there later to day... we put a lot in that thing going on trip on our trip this last spring we had over 2000 LBS in it and it pulled great! and we got about 14 MPG with the 12 passenger van(which is doing great!) oh and it is a single axle and as someone on here said for just taking bots places thats all you need! as far as a team trailer i would say(like lots of people have said) one that you can get 2 or more robots in and tools and all that fun stuff.
hope this helps a bit