I got a prototype done. There were a few iterations, but the rough one made from wood works well enough to prove the theory.
A few things I learned, I originally planed to make this out of 3/8" steel, but that is just a little to thick, so it will be from 1/4". My sketchup model appears to be off a little bit (measure don't make assumptions). There is more room around the arbor that I thought. The tops off in this video but there is about 1/2" between the top of the table and the top of the arbor so I can make a larger ring and trap the outside. originally I was going to have some wide head bolts trap on the ring (the arc slots in the sketchup model were the clearance slots for the bolts). But the trap design is better. This is hard to explain so I will be posting pictures once I make it.
I'll have to have a few custom shoulder bolts made, other than that nothing to complicated. The prototype also showed me that I need have some way to adjust the pivot arm if I am off a little. I'll have to put some thought into that.
I need to make a few adjustments to the mounting plate. Nothing radical, trim a few places for clearance, remove some excess, but the basic shape appears to be a good one.
Next step is to make 1 or 2 more prototypes. Once I have the design finished then I'll need to find a machine shop to make one. Hopefully I will find a hobbyist machinist who wants one for their saw and will make one for free!