Any advice on how to go about sizing for 29er plus? Normally I'd just go with whatever's biggest since I'm 6'4" but just for the hell of it I'm thinking of adding a BD 29er+ SS to the stable and I'm presented with the option of a 20" and a 22". Looking at the geometry chart the 22" looks absolutely massive, with a 635 effective top tube on the 22". Any thoughts?