Hot sauce.
The towing arm is one of those brackets designed to store canoes and such on the wall of your garage - a mere $2.99. It's quite rigid and held onto the frame with two bolts.
I found it sturdy enough to tow my 170 lb. friend around the driveway, and then ride it about 5 miles for a lumber run - I picked up more 1x3s to make the upper frame. I also hit up the dollar store for polyurethane coating and caulk for waterproofing (both really cheap). Weather permitting, I'll start to assemble the upper frame tomorrow morning.
