This is what i came up with for an adjustable rocker table. I was tired of creating different blanks, and made this up. Seems to work really well and wasn't too expensive. I used 2x4 1/8" steel for the 3 6' stringers. Then have 1"x1" crossmembers at 32" wide to adjust the rocker. On the 2x4's I welded nuts to adjust the bolt height. Bolts are 1/4" x 4", with the last ones being 6" long to keep a continuous rocker line. Bottom hole in the stringer is 3/8" wide while the top is 11/16" wide to allow the bolt head to pass through to the lower hole. Easily adjusted with a cordless screw driver to turn the nuts. On top of the table I have 3/8" underlayment, then 1/8" plexi. I use 1mm drywall shims to create the concave desired. Once the clamps are on the system seems really tight and solid.
Hope this helps.
I'll use your setup, but build it in wood. I already have all the materials...
What's that rooe doing on the picture with clambs?