I'm 6'8", and have a 43" chest.  I wear a Large Tall, and could probably use a Large Extra Tall.  (Not an Extra Large Tall, which is too wide for me.)

I ordered a Large Tall of this shirt.  I'd call it Extra-Extra-Large Extra-Tall.  It's very long, and perfect in that respect.  It's so big across the chest that I look like I'm a six year old wearing dad's shirt.  If this was 1995, and I was a basketball player, I'm in luck.

Quality of the shirt looks good, at least, and the length is awesome.  I'll probably have a friend take in the sides, and get some use out of it.  Five stars... if the sizes were anywhere near accurate, or if they sold a Small-Tall, if such a thing exists.