I've used a homemade 2-wheeled trailer to haul heavy loads on logging, mining, and forestry roads with motor vehicle restrictions, locked gates, or accessed by water only. By heavy loads I mean inflatable rubber rafts or float tube with chest waders, normal camping gear, fishing gear, hunting gear including rifles etc., and a deer carcass. Total weight sometimes exceeds 140 lbs. on the trailer. It's only possible when using panniers to weigh down the bike as well, especially the front end. Other than the obvious problem of ascending steep hills, braking while descending can be very tricky. On the worse grades I will dis-connect the trailer and make 2 trips for safety reasons. If I could keep the weight down to the bike's ability to handle the load, I would much rather just use panniers. On non-maintained or partly washed out back-roads, it's difficult to miss all the deep ruts or boulders with the trailer wheels. I've seen some very nasty incidents on mountainous paved hwys. where cyclists using trailers have got carried away and allowed themselves to go too fast while descending, started fish-tailing and lost it, scattering themselves and their gear all over the road.