I know it’s more work, but to add a compression sleeve you would just drill the holes out enough to have a piece of round tubing with a close inner diameter for the bolts and weld it in, cut the tube to slightly over the length of the inner measurement of the tubing to give you room/land for weld. And boxing all your open ends of tubing will increase the structural integrity of that square tubing allowing you a smaller gauge over a non structural aesthetic end cap. That is all I really have to harp on, the design is awesome.
|