Yes the 510.523 was undoubtedbly among his Heuer favourites and one of his all-time, all-brands one from what I remember.
It has become one of mine as well since I've owned one, it's an amazing watch.
And I have become a L5100 nut myself - I dedicate my wearing a Heuer 510.500 today to Chuck's memory.

Never having had the fortune to meet Chuck, we did exchange a few e-mails and he was a very kind guy, always ready to help a chap out about a watch - actually, a chronograph.
We have wonderful hosts and contributors on the Internet now, but it is very hard to come close to the passion he put, always going the extra mile and contributing so much to so many places.

I definitely can subscribe to the famous "Chuck-made-me-do-it" tag line for a few of my purchases, and I can safely state he was the one who unawares tipped me over from watch owner to collector.
We surely miss him, and indeed he kinda lives on in the many fora he helped to start or contributed to flourish.
Fabrizio