6'4" buddy we call the wookie.
Rides a XL banshee prime 29er
Fits him nice.
at 6'2" i found the L prime to fit perfectly, so yeah i'd say the XL would be a good fit. damn stiff frame
i saw an absolute GIANT riding a ventana on the ssc a few years ago. he'd have been over 6'6" easily, said it was the first bike he'd owned as an adult that fit him
this one i recon: http://www.ventanausa.com/bikes/el-capitan/
my brother-in-law rides an XL santa cruz heckler that i found for him: he's 6'6", probably weighs between 225-250 lbs and rides pretty hard; despite it being unfashionably short in the reach department he finds the frame comfortable and hasn't managed to break it yet :)
"Nobody really gives a shit that you don't like the thing that you have no firsthand experience with." Dave