Brandon's comment below reminded me of something that I've been curious about for the past three months....
Over the years of racing SM, many drivers have complained about how close their heads are to the down tube of the roll cage. A few people have sustained brain injuries and concussions from how close that bar is to their heads - myself included. I'm 3 months into recovery from a concussion I sustained when I hit a tire wall at Laguna at around 3Gs of force.
Ages ago, I saw the Supra below at a track. It was built by Twins Turbo down in Los Angeles. It has a kick out near the drivers head for more head room. Wondering if we can do something similar in the Miata. It would probably require cutting a portion of the hard top but it would be worth it from a driver safety perspective IMO.
I'm 6'3", 225# and fit in Old 48 with this seat but my head wasn't low enough ("in the bars") and I received a head injury in a collision which is why I'm building a new car.