Weimedog, I think the 520 EXC is going to be just fine for Colorado single track riding, with some work. Can't say positively yet. At first, bike was positively terrifying, threatening to spit me off every pebble or wheelie on my head, or stall off the bottom. But it responded nicely to suspension adjustments on both ends. Bike has several problems for slow trail riding, but all seem solvable. Fan kit keeps temps under control. Too much compression damping at each end for crawling over rocks, and still geared too tall. Clutching the 520 is more work than it needs to be. A 13T countershaft sprocket was a big help. I think along with a 51 or 52 rear, throttle control in the gnarly stuff will be an option again. Getting the rebound settings matched to the lower compression settings lets the bike hop over rocks on the steep inclines, and keep the front wheel down. On steep downhills, the bike negotiates the rocks without kicking the rear or overloading the front. So...I'm happy with the suspension now. Two issues I'm still working on, seat height and tall gearing. Lower gearing multiplies the inertia (flywheel effect) as the square of the % change. So even the 13T countershaft makes a noticeable difference in reducing the stall tendency. The lower gearing tames the abrupt power delivery. The other issue, the seat height I'm leaning towards shaving the seat foam. Work in progress.