I do like the idea of defaulting to the lowest gear when you break a shift cable or shifter. Both of which I've done. While mountain biking. Far away from the truck. A 24x12 is a 53.1 inch gear on a 26x21... it'll get you home, but you will not enjoy it. (At least, I didn't. But then, every time I build a single speed or fixed gear bike, I think that this time, I'll actually like it. I never do.)

--Shannon