Honestly not a good idea. If you key up with the antenna outside the car protects you from the RF. If you keep up at 100w inside then you have at that RF in the car. Not only not effective getting out but also exposing you.I was thinking of mounting the Tarheel inside my Bronco with the whip sticking out the side… if a EFHW works as an inverted L, why wouldn’t a screwdriver?Honestly I was thinking if you are driving sacrifice the cheaper antenna.
What about a bumper mount on the front Aussie style? That keep you from hitting things on the side of the vehicle and you can use it to know how much height clearance you have :)