[Antennas] mobile antenna question

[Gary Lee]

Going on a fishing trip next week.  Planning to take the k2 along.
I have a large three magnet mount for the top of the dodge ram pickup.
I also have a hustler 40 meter antenna.
In the past, this setup has performed poorly for me.
My idea this year is to run a wire from the mag mount directly to some 
screw on the body of the truck to improve the counterpoise.
It seems to me this should help somewhat.

Since this is a once or twice a year thing, and not my truck, can't drill 
any holes.
Anyone got a better suggestion?

Thanks for the help.