The general consensus amongst racers of faired recumbents is that there isn't a significant disadvantage to shorter cranks (assuming you've adjusted the gearing appropriately, and the rider is used to them).
Not sure if that still holds when you aren't getting the aerodynamic/weight benefit of a smaller fairing to more than offset any biomechanical inefficiency, thobut. There must be a point where cranks become 'too short', but I'm sure it's a lot less than 155mm.
FWIW, I'm 5'6" and have until recently been using 155mm cranks on my recumbents. (I've switched to a 140mm left crank to prevent overextending my shorter leg. It's stopped the Achilles pain dead, but I'm still getting the hang of the change in gain ratio.)