22t cogs are readily available from EAI and Surly, and I'm sure someone out there makes bigger ones. 72/22 would be about 86 gear inches with a 700c road tire, which isn't that extreme. On the other hand, 72/13 is about 145 gear inches. yikes.

Wasn't a speed record set on a stripped-down track bike with an 80 or so tooth ring one time back in the day? I remember seeing a picture of it sitting in a museum somewhere in this forum.