I find shorter chains (hand to armpit or a little less) more forgiving when I want to have a lot of body movement while spinning, though the rhythm is different. Normally mine hang to the ground with my arms just slightly bent, but I'm finding I like them shorter the more I spin with them shorter than that.
My friend Popo is about 6'2" tall, and his chains are MASSIVE. I'm teaching him and he hasn't lit up yet, but it looks incredible when he's spinning those big honkers around. 
I'm planning on making one really long rope or chain to spin with when summer rolls around, so I can develop wraps and wrap/release moves. Should be fun.
Peace, Love, and Fire.
-Rick