george900954 wrote an answer about Osprey Packs Argon 85 Backpack - 5100-5500cu in on May 31, 2011
I'm a big guy too (just not quite as big) at 6' 3", 265 lbs (used to weigh 310), 42" waist. I scoffed at the thought of getting a Large instead of an XL but when it came down to it, the L fit *ME* better (I'm fairly proportional too, though tend to be a tad more leg than torso). I was even more surprised to find the L hip and chest straps fit rather than having to go with the XL too.
As an avid cyclist, I'm accustomed to having all my outdoor gear ideally sized for people half my size forcing me into 2 and sometimes 3XL (or 7XL Euro-size!) shorts and jerseys. The Osprey's size was quite a pleasant surprise.
This is all to say that fit is everything. Before dropping the bills online based on preconceived sizing notions, you might want to try some out in person if you can. To be sure, my intent was to do just that- shop local, buy global- to save some cash. But I lucked out and was fortunate enough to find this pack not only in my size locally, but on sale too!