Re: Trailer from scrounged shopping cart
One note is that will be heavy trailer empty.
Good for not tipping over but you best make sure you have really good bike brakes if not trailer brakes if you plan to load it, really, ever been pushed through a red light intersection jackknifing in a 2 1/2 ton truck towing a 4K pound fork lift when it's surge brake failed?
No fun, and it would be less fun on a bicycle because the trailer would just keep going and take your bike for the ride.
(after a few moments of thought)
I can't think of any reasonably priced way to put brakes on that trailer, not if you want to un-hook it often, sorry, but just consider how you are going to stop the thing in your plans as it would be a bummer to wreck with a load behind you ;-}