One more issue I see with running long antennas.
The extra length going up the tube is just folding over at speed anyhow.
The receiver antenna works considerably better and is meant to be vertically polarized. You ever watch a long antenna tube at 60 mph.
The long antenna tube is bowed over and your long antenna is not an iota taller than the shorter one was and it is laid over flat not sticking up vertical like it should be.
The tube is laid back with the end horizontal and back over or closer to the prop roost.
4-6" straight up or a 8"-12" folded back to the same 4-6" height but now it is laid flat.
The straight 4-6" one is going to give you the better range.
Noticed I haven't almost poked the ole' eye out since we got rid of those long stranded wire antennas the FM radio used to have to have.
The short antenna was all the rave of the 2.4 GHZ. Now you want to go back long for no reason whatsoever.
Decrease your range and maybe poke your eye out too. Nice.
The short vertical antenna will have better range than a long antenna when underway at speed.
I've always ran vertical whip on boats and rc cars that can flex.
With stage wireless mic systems we run receiver antennas at 45 degrees relative to vertical as nobody holds a mic vertical. Model aircraft don't use vertical antenna orientation.
Boats are a different animal relative to the RF as they operate on the water. Nobody I've ever seen has held a transmitter with antenna in a vertical orientation. Position varies on transmitter antenna from near vertical to near horizontal - somewhere in between. Worse orientation is transmitter antenna pointed at model, which is easy to do with aircraft.
Speculation for me would be 45 degrees on a boat would be closer to optimal to align with transmitter antenna. Being so close the water vertical as you state may be best for boats. They are a unique application for sure. Just for the record, perpendicular orientation between receiver and transmitter antenna is the worst possible condition.
Something else to think about for sure.