5' 11 i me boots 170 on the DH, I have 175's on my play bike but, they're from a 4X rig. I had 170's on my trail rig as per crank length calculator but, then I got a too good to pass deal on some XT's £20!!! so I put them on depite the extra length. Really want to go back to 170's as my AVG speed is down since.
160mm Primo Churchills. Not because I'm a huge primo or Stevie fan, but because the cranks are bomber and I when I switched I couldn't find any other options other than Fiend, which I'm not a fan of the extra lock bolt they use. I'm running 160's on both my bmx's. I did feel a loss in torque when climbing or riding in soft dirt, but overall the seem great with bikes with short chainstays. If I had a bike with 13.6" stays or longer I'd be on 170's still.