165 Cranks...who runs them?

It should be calculated relative to your frame (body not bike) and to what you like.

I hate when people engaged in sports succumb to the limited range of motion in their joints, that, my friends, is a slippery slope.

Peace

It should be calculated on efficiency and what feels best. This may or may not have anything to do with your frame. The problem is this would take a lot of experimenting and a high cost, which I guess is why people just stick within the limits of the mass market.