The extra height plus the considerably reduced coil size makes quite a difference. And remember, the higher it is mounted on the vehicle, the less ground loss it will have. One Hustler mast resonates about 49 Mhz. Finally, the spring was abandoned all together. I took a 10 meter resonator and band sawed out the insulator and coil.
The magnum SLV now used a large radial system and a modified VersaTuner as a base matching network, with no coil on the pole, just a heavy braid element 26 feet tall.
Hustler RM40S 40 Meter Super Resonator
It greatly assists with getting the mounting vertical. I have used lengths from 18 feet to 30 feet. Bumper mounting makes for a very asymmetrical counterpoise. They were well clear of trees etc. It takes down quite fast as well.