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As well as grip (and I agree weight on the front is good) there's being able to ride the bike for the time you want to without hand and neck pain. If you plan on doing rides like SDW then be cautious about getting too heavy with the hacksaw - what's fine for 2-3hrs can be hell for 12. One way to give yourself flexibility is to test with the stem negative rise - if you've gone too far then flipping will restore height.
Also don't forget that standing on the pedals with your hands on the bars (ie attack position) forces you to raise your head to look ahead ie testing on a non tech ride might lead you to slam more than you should.
AdsH-
Was definitely wary of testing it for anything less than a few hours riding before doing anything permanent. My normal rides are generally 30km of road/towpath then about 4-5 hours on the trails the 30km back home again so hopefully will be a good test.
And thankfully I've stopped with the endurance MTB riding!
mmccarthy
I'd just slam it, every 29er I've ridden has felt lofty and ponderous so as low a front end as possible will load up your front end up for greater grip and counteract your weight shifting back with the short stem. if that's too low to pop the front up then lift it a touch or just try harder. Wide bars will also bring your weight forwards, but be mindful of the purpose of the bike, you probably don't want DH bars if it's an xc beast.
It looks fast anyway.