Video
Here is a rendering of my new design. I have just gotten back from QU-BD. They were generous enough to laser cut all my parts. I am now frantically printing out the remainder of the parts. (I hate plastic that isn't spooled. I am probably 8 hours behind due to rat nesting killing some of my unattended prints.) This is a very ugly design in my eyes. I think it will work but I hate the complexity. It does have the benefit of side stepping the torsional rigidity issue. I may grow to love it. Who knows?
My previous design is very elegant and I am going to revisit it to see if I can achieve the torsional rigidity that I need to make this a 3D printer. A few simple tricks (namely creating a unibeam instead of two uncoupled pieces of 1/4" flat stock) could increase the rigidity by a factor of 10. That has the potential of reducing the 5mm play down to .5mm. I definitely want to try that out before I give up on its simplicity.