Sub-frame connectors... Please build them correctly!

I'm in the process of building a set of sub frame connectors. I used the page from bigblockdart.com, and built them. I didn't realize that I would have to notch the floors to get the 3"x2" tube to fit flat. I don't want to notch them, so I'm going to opt for a smaller tube, with a thicker wall and weld them to a 3x2 box that fits around the rears.

Some good points on both sides here for sure. I think I will build some gussets or some plates to attach the floors in a few place as well.

Any thoughts?

Will post pics along the way.