Whats the consensus on optimal crank arm length for road racing, is it really worth spending an extra grand on custom crank arms or are the stock ones good enough for most riders. Ive seen some pros swear by 170mm, while others claim 172.5mm is the sweet spot, but what about for us mortals who dont have a team of mechanics tweaking every aspect of our bikes, is it really worth the investment or just a bunch of marketing hype. And what about the effect of crank arm length on aerodynamics, does it even make a difference or is it just a minor consideration in the grand scheme of things.