I bought a black shirt for my very tall and lean 16-year old to wear for stage work -- and was delighted to be able to get his size (normal neck with extra-long sleeves).  As some of you know, this isn't easy.

The fabric is 65-35, which isn't the best, as some have noted; the reverse ratio (65% cotton) would have been a lot better.  However, assuming that this is acceptable, the shirt doesn't leave room for much complaint: it looks & feels good, and it falls nicely on a lean frame.

One amusing note: the shirt was likely packed in Asia somewhere: you can tell because there were something like 9 pins holding it together.  Be careful when unpacking!