ok. this is what i have figured out for mine. i am doing a 2x2 rib and starting with the long rectangle and binding off everything but the middle then working that for x length then binding off and seaming (although i have been thinking about PU sts and k2tog for the middle part like you do when you turn a heel- if that makes sense). but as far as dimensions go i have discoved that C
needs to be the circumference of your upper arm and A
need to be the same length cince they have to be sewn together. as far as what that length is.. im not sure. but im going to try about 12". i am about 4" into this. i will post as soon as i finish.