I'm not sure which part of my rambling speculations you're referring to really (e.g. the F-500 part?), but the SRF isn't an open-wheel car. It's small-ish and open-cockpit, but closed-wheel, and it can get along in a regular group and do normal passing signals, etc. Size-wise it's comparable to a topless Miata. And yeah I'm running in the advanced group with my Z anyways.
Assuming this link works correctly, this should jump to 7:00 into this video, where I'm following (and eventually passing) an SRF and Miata: makes the size comparison obvious:
https://www.youtube.com/watch?v=Mo6lxgJqiBw#t=420