+1 for the Kirkey Intermediate Road Race seat.
I sat in an 18" Butlerbuilt with a sprint wing bolted to it and it fit me like a glove. I asked my cagebuilder and got a very nice deal on the 18" Kirkey. Never sat in one ever.
Initially felt a bit tight, however, on the track, it was such a HUGE positive to my comfort that @ Nelson Ledges, I took fuel on twice (that's 2hrs of racing BETWEEN each pit) before I managed enough fatigue to feel anywhere near the 1.5hours in an OEM high-back sport seat with decent bolsters.
If you're near NW ohio/SE michigan (i suspect you're not) I can get you in touch with my cage guy and he can beat pretty much any of the big names online (summit, jegs, etc) for pricing on them.