i run 42/16 with slicks, 42/17 or 19 with cross tires - in vt. i'm not climbing mountain passes - but 8 and 9% grades and sharp rollers on dirt roads.

i've been running the dingle cog in the back, and instead of removing the 40t ring on the front (used with the 19 cog for studded tires in the winter) i just moved it to the inside, so now i have a double dingle or quadilator.

the bike has morphed from a road fixed to winter studded fixed to a moderate trail rider to what i hope will this year will be a dirt road / trail camping explorer bike. i'm burned out rando riding on my geared machine - and the fixed is just what i've needed to snap back.

currently i'm running:
42 17 or 19 (dingle cog)
40 19 (studs or mild trail fixed)
40 22 ss freewheel (new, but for dirt, and if its really climby with long descents)

the freewheel gets used in the dirt or when its really climby - and i just put it on - the original ss i had sat on the wheel for 2 winters and was siezed up.

if i plan on using the bike for distance (did some long rides on it last year and a century on dirt / paved) i'll run 28 or 32's and put on the 16t cog (or just run it in the 17 on the dingle)

bike is a crosscheck, and i can quickly swap from drops to mary bars.
and i don't think i've ever flipped a wheel or changed cogs mid ride.