I'm looking at purchasing a new fox fork (f29 RLC 100mm) for a Niner frame. I've read a lot of post talking about how the 15mm thru-axle is superior to the "old" 9mm qr standard. Fox claims that the 15mm is 25% stiffer. I guess I can understand that the axle itself may be stiffer since it is larger (even though it is probably hollow to save weight). However, I don't understand why the fork legs themselves would be any stiffer. The lower legs are locked to the front hub with the 9mm or the 15mm. So why would the 15mm be so much better? I'm sure I am missing something.