I'm going to jump on the Tom Biliter bandwagon as well. He'd definitely be the guy to talk to.
Also note that, in the image Sir Ian provided, the sleeve isn't just a straight tube. It bends upward around the elbow, and you can see there's a bit of an angle in the join there. What it looks like to me, and what I've found from re-tailoring my own hauberk's sleeves, is that if there's too much extra bulk on the inside of the elbow joint, it will bind, so it has to be shorter than the part of the sleeve going around the outside of the elbow.