In my spare time I've been piecing together a pair of mail voiders for my kit, but I've come up to a snag on the connection of the sleeve. I tried to construct the turn as two L shaped strips of mail, but when i tried to connect the two along the sleeve I realized that the two pieces run in opposite directions to each other. So how are the sleeves and top constructed on a mail shirt so that the mail aligns correctly?

You just continue making it go the same direction on the sleeve as it does on the body. Just close the rings on the body part together, and the rings on the bottom of the arm together. (The last ring in the armpit will probably go into either 3 or 5 others, not 4) It's difficult to describe, but actually very simple.
Look here
http://www.allenantiques.com/images/M-16-overall.jpg