DV27's were ok in there time, but they are not ideal.
you need to go something as physically long as you can, with a wide ope air spaced coil, ideally spring loaded.......
it needs a good electrical connection to the van body, (So not a magmount) AND keep the coaxual as short as possible....
check out the orbitor and stainless guttermounting from thunderpole
removed double post bloody admin trying to keep us mod's busy