So you want shorter crank arms - now what?

 
Continued from Are your crank arms too long?
Ok, I have decided that I want to replace the standard 170 MM  cranks on my Slipstream with 155 MM cranks more appropriate for my Hobbit legs.
So I Googled and found almost nothing. Looks like the shortest commercial Road and MTB cranks are 165 MM. There are 155 [...]