Hmmm. Does that work better than a matching balun? Or is that basically the same.What helped me was making a RF choke with some coils of coax with ferrites on them.
I know Jeeps can be tough to get a good tune and I've only been successful on a jeep with a 102" whip, spring and pucked to the roll bar. Multiple ground straps on everything and then trimming whip or coax.
11 meter tune that is.