Thanks, Sandy. Your real-world experience and insights are really valuable.Why Trolleys Break
There are comments about breaking trolleys. I'm not surprised if people build weak trolleys as shown on the web.
I think your idea of the 'S' threading of the straps is very clever. Also, the legs storing inside the supports is less cumbersome than the flip-down style.
Some of your comments about the defects of commercial trolleys (aka carts) would be useful. It seems that a lot of the carts broken on the Bowren portages were commercial, not home-built.
I had a C-Tug and it seemed difficult to assemble and disassemble, so I re-sold it. But I am not a 'cart guy'.