Isn't the average length about 5.5 inches? An extra inch and a half wouldn't make a big difference when ttc, it's really squirted out quite quickly and far, he'd still be able to get it to the right spot!

As for orgasm, while it does help it's not essential for conception. Also, it's very common for women not to orgasm from penetration alone - I sure don't! The nerve endings in your vagina that make the penetration feel good are all towards the opening, I think in the first three inches? So really, he shouldn't need much more than that! Personally, my DH is fantastic at getting me to "go" in other ways at the same time.

Good luck with ttc!