I just finished building my rotatable dipole as per K8BP in the May 2007 issue of QST magazine. It uses two of the MFJ-1954 10' telescopic whips. I changed a few things such as the way the parts go together. I substituted screw fittings for the sheet metal screws for durability. I still have to put a balun on it and for now I am using an air balun made of wound coax but as soon as I can get some toroids I am going that route. I put it up for the first time today and right away I was able to compare it to my tarheel in that I could pick up stations that I can't with my tarheel. Kind of wish I could leave it mounted when I drive but I don't think it would survive an encounter with a bridge.
And don't worry, K0BG, I take it down when I drive. (sorry, I just couldn't resist)
Here is a photo of it mounted.http://img155.imageshack.us/img155/1091/picture022ng3.jpg