Not a structural engineer, but I would be concerned with those alum rings. It looks like 1/8 X 3/16" at the thinnest point. I struggle to see how aluminum of that size could hold up to the loads imparted during a strong blow from a T storm. The plans use 3/8" dia steel, threaded into a .5 X .5 X 6" chunk of alum bolted directly to the thick part of the spar. At least they did on the 6 and the 10; cant speak to the 14. Hard to tell from the pics, but look like it is using thin support material rivetted to a thin wing rib, possibly tied into the thin spar flange. This appears WAY less structurally sound than what Vans designed. Certainly not saying it won't hold, just saying that it seems substantially under engineered comparied to the original design.
I may have not fully understood your intent. Possibly you use the stock tie down rings in strong winds and these are just for burger runs in good wx. In that case, it is a neat approach. I just leave the rings in the tool bag and install them when tying down away from home when chocks alone are inadequate.
Larry