I used short cranks (170mm) on my TT bik. I noticed, SRM data, an improvement in my power. It’s hard to say if this was because of an increase in form though. So I compared 20 min efforts TT vs road bike and TT looked better compared to the road bike I didn’t change my cranks on. So… I went shorter there too. I’m 6’2″ on a 58cm frame.