Which frame rail connectors to use?

I used plain old 2x2 steel tubing and liked how it worked out. They came through the floor about 1/4" high and probably 6"-8" long. With the carpet down, you don't even know they're there. I think that the steel cost me about $20. Not a big fan of the ones you are thinking about using. Square steel tubing has got to be , what, 10 times stronger in torsional rigidity than a stamped u shaped channel? The reason for the connectors is strength, not ease of installation, even though mine were probably lots easier to install the us car tool ones. lots of grinding and welding and fitting to do there. Why do extra work for a questionable result?