FM radio is circularly polarized, so it should work fine. think about it, most modern cars used horizontal antennas in the rear window or across the top of the windshield. the polarization shifts as it reflects, so for FM receive antenna polarization is not as critical as part of the signal will be properly polarized in any plane. it is just a matter of whether it is horizontal/vertical/somewhere in between at the point you measure it. move a few feet and it may swap. the very brief pattern they showed did not look to have too much degrade thru the car body, most likely due to the soft top so the only real obstruction is the windshield frame.