I'm setting up a single speed 29er and Jenson has a set of 180mm XT 10sp cranks on sale - I'm a large rider and would like a tad longer crank. Can I use the existing chainrings w/the surly rear cog I have or do I need a 9speed specific chainring? I assume they're still a 104 bolt pattern - will it really make that much of a difference on a single speed? How about bolting on an aftermarket ring like a blackspire or e13 (which state they are 8,9,10 sp compatible)?