Passing will be point by on the straights. Zip tie to the frame rail would be the best option [for mounting the transponder].
I have a hard time placing "time trial" and "pass with point-by" in the same sentence, but whatever. I'm going to tentatively plan to do this. I might do the Santa's Run at Atlanta Motorsports Park next weekend, if a spot opens up. If I survive that and my pads/tires are still good, CMP is a definite. Else, I'll do CMP, anyway.