I don't know how I missed this yesterday, but anyway..... here are my thoughts.
DO NOT bring up anything having to do with penis size with your man, ever. I have read literally hundreds of stories here from guys who could never forget just one casual mention of their size by a girlfriend or wife or lover. Often what seemed like no big deal to the girl ended up crushing the man and destroying whatever relationship they had. And guys never seem to forget conversations about size, even decades later.
I really don't think women can ever understand how tightly the male ego is tied to his cock. If your man is small, he knows he's small, but he probably feels fine about himself since he's in a loving relationship and having regular sex. Unless you want to send him spinning into depression and anxiety, DON'T BRING UP PENIS SIZE AT ALL.
However, there are lots of ways you can nudge him to discovering this site or other similar information. I think the best is to stay as far away from cock size/hardness as possible. How about raising the possibility that he might become multiorgasmic? A lot of guys here are experimenting with DOs (dry orgasms) and working to become MMO (Male Multi-Orgasmic) using kegels and edging and other PE techniques. There is a whole group here (search under "Groups") on the topic, plus many threads. If you could get him interested in looking into DO/MMO, then he would also come across all the size-enhancing material that is here as well. Anyway, that might be a safe way to introduce him to the PE world.