George, thank you again for all the great info. The historical context is really interesting to see. I will keep this info in the back of my mind and now I have it in my thread for future reference.
I need to keep in mind that my primary concern is a well handling frame with good suspension, stiffened structure, and great brakes.
To that end, I ordered one of the RPE cast iron rotors in the drilled flavor that will be mated to a custom billet carrier. Why? Because I can!
I need to come up with nice master cylinder that fits the ratio outlined on Vintage Brakes, which looks to be 11 or 12mm when mated to a single Grimeca opposed piston caliper, which is on the way from England as we speak. Any suggestions there that won't cost a small fortune?
Here is a shot of the mockup caliper on the old disc. I am waiting for my 4-bolt Grimeca and rotor right now.
Next up is getting geometry set in that magic trail sweet spot. I am going to have a set of mock trees cut from HDPE so I can have the frame sit up on its own to get measurements.
I plan on going about 1" over on the rear shocks to steepen the neck angle and with the mock up trees in place I can bring the trail back to an ideal range. Since I am using GL1000 forks and they are longer than stock I will have some adjustment there as well by sliding the forks up and down in the trees.
The plan for suspension is full Race Tech with non-reservoir shocks out back (per AHRMA rules) and springs/emulators up front.
The frame will be going to the welder this week for round one of the bracing process which includes the gussets I showed earlier and having the upside down "U" where the down tubes meet welded up. After that the rear hoop will be modified by removing the stock stamped one and adding a low tubular hoop in its place so I can mount my seat with a pivot as bwaller did for his race bike. Its a simple design and seems to work well for him so that's my approach as of now.
That pretty much covers the handling/braking aspect unless there are other suggestions from racers out there on what I might be missing.