Interesting - all 3 C2s in the pic are using center sheeting. I appear to have the same stack as USA 70 - 4 on top, 4 on bottom, with a tie-off through the center of the bottom.
BTW - I can see the downwind sheet management a bit as you described in your pic here
As for the boat, you're close - mine is hull #224. Purchased from Dan K out of Omaha, NE. He did a nice job getting it dialed in for me

it has proven to be really quick upwind. Still working to get my downwind technique perfected though.
You guys are obviously at a different level than I. I'm still well on the learning curve regarding the finer aspects of getting the best VMG out of the downwind run (but that's a whole 'nother thread).
Curious about the spin sheet takeup method you mentioned. Do they cross the tramp at a diagonal, diving under the aft part of the tramp? Which grommets do you use?