its possible and i've hit one before, all it is, is just a down flat down set up with the down's more mellow so the flat is actually and up... just fells the same as a dfd though...
i could not find any pictures, but those of you who rode Brighton way back in the day, there was a DC rail, where below the rail was filled with shoes, and if i can recall correctly, it was a down,up,down. but fairly mellow through transitions.
I hit one last year at Adstock. It was supposed to be a FDF but they set it in a UDU. I've been able to do the up down part but as soon as I came on the down up kink, I lost both of my skis and fell directly on the box. All my friends tried it after and the same thing happened to them, it was just impossible to make.
duuuuuude! this is the first thing that came to mind when i thought about the kink issue. but if you just make not steep sections it should work fine...
and THIS rail on the other hand, i saw one person go for all year, a fatass snowboarder probably from edmonton hit the kink toe edge and smashed his face, ouch.
i went for it and jumped off before the first kink. its so freaking high and poorly designed.