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The problem with just bumping up the FD on the Miata is that the engine doesn't have a lot of torque to compensate and you'd have to put really large tires on it to make a substantial difference in acceleration. If you drop from 4.1 to 3.9 on the FD with stock tires, you get 12.23, 7.36, 5.19 final gear ratios for 1, 2, 3 respectively. If you go from stock tires (~22.74 diameter) to, for example, 205/50-17 (Mazda 3 size, although I know the wheels themselves are incompatible) you end up with 12.86, 7.74, and 5.45, all shorter ratios still. And that's only figuring on dropping from 4.1 to 3.9. I would like to go to 3.636, but would have to lose way too much weight to compensate. Instead, the '87-91 RX-7 has shorter low ratios and taller top. The final gear ratio results without a FD change and stock tires are: 14.25, 8.21, 5.6, 4.1, 2.83 vs. the original ratios of: 12.86, 7.74, 5.45, 4.1, 3.34. As you can see, the RX-7 transmission allows for much better off the line acceleration and lower rpms in 5th.
My plan was to instal a standard-looking single roll bar behind the seat, where it should fit under the teardrop canopy before it tapers too much without having to design the canopy to be too large proportionately with the rest of the body. If not, I may try to incorporate it into the fixed vertical hoop that would make up part of the frame for the 3-piece windshield, but I'd rather not have to do that. Welding 2 steel bars in place of each door and front to back down the near-center of the original cockpit should easily banish the cowl shake that makes me generally hate open cars. I just wonder how much weight I would end up losing in the end since the Miata doesn't have a real lot of glass to lose and the passenger seat and top are probably minimal as well and be adding back some extra bodywork and the remote-activated power mechanism for the canopy. The idea was something like a single-cockpit D-Type Jag or Lotus 11 with an enclosed canopy (which I believe Lotus made one of with a canopy as a LSR car).
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