Seat position, bar position
Funny, I'm 6-foot-3 and finding that having the bars in the lowest position and the seat in the low position works best for me. This is really surprising, in that a big reason I bought the bike is that I liked the tall seat and short, upright reach! I have a peg-lowering kit on order that it's possible I may not even use. The old GT caused me to cramp up, even with bar backs and peg-lowerers. What's great about this GT is that the seat can be changed in a few seconds, and the bars are also easy to adjust.
The moral of the story: take advantage of the adjustability of the GT and try a lot of different combinations. You might be surprised by what works for you.