I am not a structural Engineer but after looking at some of the Photo’s of Sub frame connectors I was wondering if you just wanted to strengthen the under carriage if you stitch welded, Say 2 OD x .120 wall x 1.760 ID tubing along the inner rockers would that help any with flex I like how the Spohn sub frames get welded… Like the UMI for tie in, But the UMI look to far from the rocker for Stitch welding.
Any Thoughts?

 

1.75 OD fits better. Go ahead and make your own, make the best of both worlds

 

I dont have any pics but I did very similay to what you are saying. I stitched in 1/2"x1.5" rectangle tube front to rear along the entirelength of my rockers (except for the several inches in the passenger side where the exhaust routes), and there I did a piece of 5/16"x1.5" plate in place of the tube.
Very rigid, I can jack the car now and no matter where I start front or back and both the front and rear wheels come up at close to the same time.
Makes for a handy jacking point too. Havent tied into the lca mounts in the back yet and I am not sure I need to. Car is very rigid

 

Global West connectors may be the ticket to ride for you - check them out...