How in the world did this thread get sucked into the recumbent forum? The OP is not a bent rider and the subject of short cranks is not bent-specific.

I use 155mm cranks on my latest lowracer. Not that I'm a convert, it's just that I need the short cranks because otherwise I can't adjust the bike short enough to reach the pedals. Short cranks give up a little bit in torque but the advantage is that you don't need to bend your knees as much at the top of the pedal stroke, meaning less strain and higher output in the first 1/4 of the circle. To compensate for the torque, you have to spin better, which may mean lower gears.

My 155s are made by Thorn. Current searches don't show any made by them that are that short. Whereas 165 are easy to find, 160 are a bit harder and 155 are very hard. Well, maybe that's an exaggeration - you can always get cheap short cranks that are made for kids' bikes. You may be able to get your current set shortened, depending on what you've got.
http://bikesmithdesign.com/Short_Cranks/shorten.html