If you get the XL model you should be fine. I am 5'11" and fit ok into the average size model fine, but the chair isn't that great though it is very usable. These things aren't pretty but they get the job done, I can sweat nearly a liter (thats a guess) after being in it for 30 minutes, and I don't feel exhausted or anything afterwards.

There is no weight on my shoulders or chest while using it, so I think you would be fine the the XL model. I usually am very uncomfortable with things around my neck but that hasn't even bothered me (the one piece velcros around your neck).

Goodluck Dulak!