After designing the pneumatic shifting system on our car and redesigning it for two years after, I'm still not convinced it is the way to go. For the same on-track performance (show me numbers) simpler is almost always better. I'm on board with UTA/Texas A&M with the mechanical clutch w/ downshift butterfly thing they've got with an electric kill switch on up shift. It just works, it's fast, it's easy to get into neutral, and I prefer that positive feedback; the ca-chunk, that says "you, sir, are in second gear now."

Also, I like Paradigm Motorsports stuff but we had one of those solenoids that was leaking and I replaced them with the industrial Ingersoll Rand ones from Grainger. Maybe we just got the one bad one, but the IRs worked so I stuck with them. Also, you can look at Grainger/McMaster and find the exact size pneumatic cylinder you need; one that fits your packaging with length and diameter.

BTW, there's an SAE paper on this worth reading.