i ride dh on mine. but i believe that the warranty has already expired so i run a DC fork anyways because there is nothing left to void. its not exactly fast but it is strong enouhg for a dc fork. and as far as being slack some good drop crowns will do the trick. and i wouldn't run those betd plates on them. it will make the geometry even worse than it is to begin with and you could have troubles with the linkage hitting the seat which is no good.
I've got a friend that races DH with one, just moved up to expert class. He runs a slider on it, never had a problem with the frame. He's pretty hard on the bike too, I've seen him case hard on it. Just about every part but the frame and fork on that bike has broken.
Go to any southeast race and check the sport class out. You'd be amazed at how many of them are out there. Am I saying it's a good idea? Depends on what your idea of fun is.......I rocked one for two seasons of DH races--one with a single crown Manitou Black and one season with a Boxxer Race. I'm just a sport rider and always will be, so I didn't take things too seriously, obviously......but I had more fun than a barrel full of monkeys. If you're more serious about your DH, then it's a no-brainer that there are waay better bikes out there suited for that application. But if you're a casual DH'er, then it's a good place to start.
Dual crown forks have been warrantied for AC's since they started the '03 production run with the Sherman Sliders. In the two years prior to that, they were not. I ran my '02 AC with a dual crown and never had a problem. But, like I said, I'm a sport rider and aren't pinning it full throttle-huck-it-for-life-brah stylee......so take it for what you will.