Thanks, FW. (Not a CE here, but EE and physics are what I studied.)
In your drawing, there is 2x4 tubing used, which can work well, but you really have
to weld both sides of it to make a good structural connection. Failure to do so resulted
in a major headache for Kioti with their FELs last decade. That is why I prefer
channel with 1/4" thick (min.) webs.