Update:
I am happier with this bike every time I ride it.
I changed out my cranks twice now, and very pleased with the newest set up. The White Industries crank required a 122mm BB, which was really flexy- to the point of hitting the chainstay when I'd crank hard enough.
Next, I tried the Ritchey WCS cranks off of my Pugsley. Stiffer, but I had to space the ISIS BB over a bit to the drive side to clear the chainstay under hard efforts (again.)
Both of those were 170mm. I've been dialing in my wife's position on her bike, and noticed her XTs are 175mm, which are too long for her leg length, so I traded her.
Yesterday, I rode Government Canyon, a rocky, steep local trail. The increased stiffness was noticeable, and with the sustained, all-out effort climbs, I think I'm liking the gained leverage of the additional whopping 5mm of crank length.
I didn't notice an increase in pedal strikes, and had no problem staying on top of the cranks.
This was probably the most technically difficult climbing and descending I've done on the N9 to date. Not the steepest, and it IS Texas so the climbs and descents aren't super long, but it's tough on the single speed. I've punctured my rear tire (sliced the sidewall twice, punched through the tread once,) on the last three rides there...on the climbs!
I was thinking, as I was patching my AKA, that this bike felt like it was made for this kind of riding. Then I remembered thinking the same thing the first time I took it on our extended-rockgarden chunkfest, and on the fast, swoopy waterbar laden Boise trails, and the alpine Bogus trails...
Here's some pics from yesterday.
Los