Well, judging from the description, I'd say you need a cap
instead of the coil. It's sorta telling me you have enough
coil already. Part of your loading coil in the whip is
already acting as a matching coil. I think you probably
need a cap to tune out some reactance. I often use a
simple MFJ random wire tuner as a mobile matcher.
That would dial that down pretty low I would think.
But this is just a guess, being I can't see it...
In my trucks, I have the small tuner, and also a "dollar
special" matching coil. I use the tuner more often I
think...Most of my antenna setups with the glass stick
bases, have a few turns of matching coil wound into
the base. MK