what's up y'all -

i'm chopping this ugly old mongoose women's MTB for the upcoming Slaughterama II in Richmond, VA. It's gonna be a low-slung farthing high-wheeler-meets desert dragster theme with the 27" wheel up front and a bmx wheel in the back. I've already modified the hub on the rear wheel with longer axle and spacers etc, but here's my problem: I'm trying to use the existing rear derailleur to pick up the slack left b/c of the vertical dropout, but can't get it to line up right w/o being connected to the cables.
have any S/S conversion people ever successfully done this mod? tell me how!