Rigging for Unity using biped+bones (for IOS3+)

I am working on a project which will use unity and give the output for IOS 3+. I have developed some assets using 3ds max 2012.I will rig the characters using biped.I found that if I add some extra bone with default biped then the animation will be good. because my characters are little complex. how many bones can I use to run the game smoothly in IOS 3+ devices ? is there any limitations ?( all the demos I have seen using less bones then default biped has) how does the bones effect on game run ?