i have a 12-22 and a 13-26 cassette on the commuter and race bike respectively.
as far as interchangeable cogs would it be okay to switch out the first and last cogs so i have something like a 13-26 and a 12-24 (this is on 8 speed cassette's btw [yes i still race an 8 speed])
edit: the reason why i don't just switch out the cassette is because one is considerably more worn than the other, however the 12 tooth has barely been tapped. The commuter cassette used to be the race cassette.