I got up to about 500 pounds on my cargo trailer (including a little loaded on the bike). IT WAS HEAVY. Just a small rise in the road, and it was a pain to pedal. I have two hills on my way home, and must admit that I couldn't make it up the hills. It was even a pain to push the bike up the hills. My driveway is steep enough that I ended up parking the trailer and retrieving it with the blazer.

Perhaps I'll have to try something like a 28T chainring and a 40T cassette on my next build.

My trailer has hub brakes from a kids bike. I had originally intended to design mechanical surge brakes, kind of like boat trailers use. However, that portion hasn't been built yet.

I've decided that for flat town riding, I don't get that fast with a 500 lb road. Once I hit the country roads where I hit my hills, braking (or emergency braking) isn't needed. Anyway, something like surge brakes (adjusted appropriately) would be nice, but don't seem necessary.

I could probably build surge brakes with just about any type of brake, so perhaps one would be better off with better quality hubs (lower resistance), and disc brakes.

As far as the hitch, my cargo bike/trailer is a pair with a straight tongue, and pin hitch.

I still need to do some more work on both the bike trailer as well as the bike, and I hate welding aluminum. See photos here.