Whenever I finish climbing a hill on my overweight, one-speed klunk kreation, I always kinda wish it were lighter. If'n it had a triple tree, it'd be a heckuva lot heavier. If it had a suspension fork, it'd be real heavy and also a lot bouncier...especially b/c I have to stand on the pedals to climb w/ a singlespeed. Just something to think about, if your goal is to actually klunk it up. It might look cool, if that's your thing.
As far as folding on ya, well... ot all of these things are made equally. Most of the triple trees I see are built to a thin nickel, and I wouldn't be surprised if they folded under actual klunk-use. Others are more robust. In the end, though, if you check out the Klunkin' sites and the Klunkerz movie, you'll notice that most of those guys ran rigid forks; which'd be more authentic. However, a lot of them would've run suspension if it'd been available, but that (to me) would make me want to run an honest-to-goodness mtb suspension for of decent quality.
But then, it'd have me bouncing too much on climbs. Hmmmm.