My cello teacher is always commenting that my right arm is not relaxed. It isn't. And this is because I'm too tall. I have to scrunch it up a bit for the bow to be on the strings. It's not just a matter of personal comfort though. If I can relax I get a much better sound. This I know by putting the cello further away from me so I can relax it. Unfortunately putting it further away means the pegs are digging into my neck instead of being behind my neck. And if I try to tilt the top half of the cello away from me, then the bow is hitting my left leg on the A string. Finally yesterday found out there's such a thing as removeable pegs.
http://www.cello.org/Newsletter/Articles/jensen/jensen.htm
I think I've been relying too much on my teacher instead of reading up on my own.