Yes, I don't mean direction of car passage, but directionality of the transponder antenna to make it have higher field strength to ground direction.
For VDD measure, it can be done for sure. An aux packet must be used to send the information and to relate it to the passing transponder. I wonder if it't better to use a new 'preamble' for RCHourglass packets or try to unserstand AMB encoding (which I find difficult). Only thing I'm afraid of is that sending other aux packets might make the transponder not compatible with Mylaps decoder.