I switched to 165 mm cranks on my TT bike a 4(?) years ago. Was using 172.5 mm cranks but switched to try to open my hip angle and to allow for a slightly lower front end. Always used 165 mm cranks on the track and as others have said, I never had trouble switching back and forth. One of the few position differences that I don't feel. for reference, my road bikes have 170 mm cranks.