Tests of mobile antennae in the Amateur Radio 75 meter band (4MHz) yielded
the following results:

* Well-designed Bugcatcher or Screwdriver with top hat 0 dB reference
* Bugcatcher or Screwdriver with no top hat -3 dB
* Hustler or Outbacker -9 dB
* Hamstick -12 dB
* Whip with autotuner -14 dB

This suggests that the common insulated-backstay-with-autotuner used on
sailboats could be improved by adding a capacitive top hat immediately below
the upper insulator and/or a tapped coil in parallel (ie around) the lower
insulator to tune whatever length of antenna one can physically accomodate
to resonate on or near the Marine frequencies of interest, such as 2182 MHz.
Has anyone any experience doing so?