I've noticed this phenomenon with myself -- I definitely get bigger and bigger and bigger the more I get close/pull away, though of course there's a limit and, for me, it certainly isn't (lengthwise) close to the apparent norm for LPSG males . What I find interesting is that, for your guy, the "bigger" is noticeable enough for you to discern with your hands and pussy. (Especially the latter, which I'm sure is a magical piece of machinery but not the most exact "measuring tool" )

What's going on is that when you arouse him, a certain percentage of his corpus cavernosum (and other similar parts) is filling with blood -- which leaves at a much slower rate than when it went in. But you can "restart" the process before it's all gone with some more stimulation, which will cause the same surge of blood to his penis -- except there is some still in there, so you just add to it. Get the refractory rhythm right, as you did in the car, and you can build and build and build him and "approach his limit". Hopefully, this knowledge will benefit you both as you refine your response to each other .

Cheers,
Kevbo