Bulleteer,
Basic principle is that if your antenna(s) and the other guy's are 90 degrees out of alignment, you will lose 3dB of signal strength. 3dB is HALF of your signal, so definitely NOT recommended. The convention is for aircraft antennae to be vertically polarised as this produces a circular radiation pattern all round the plane (except if/where the antenna is screened by metal bodywork / bags of water (us) / etc.), so best to stay - as far as possible - the same as everyone else.
Regards
Peter