Taken Women - Bigger Cock - Reluctance

Taken Women:
You're free to have sex with any woman in a sexual relationship. This might even include more implicitly open relationships, such as sex friends. The bottom line is that if a woman is in a relationship that includes having sex, she's fair game.

Single women, however, have to be wooed the normal way.

Bigger Cock:
Exactly what it says on the tin. You have a bigger dick than their spouse or significant other, and are therefore more deserving or needful of their assistance in relieving it. That's not to say you have an inhumanly large cock (though you might), merely that it's measurably bigger than what most guys would be packing.

Of course, if you happen upon a woman whose beau is bigger than you, then barring some supernatural shenanigans or amateur surgery, you're shit outta luck.

Reluctance:
Of course, these women don't especially want to fuck you—that would be cheating, after all—they simply acknowledge your greater... need. Though their feelings on the matter might change if you fuck them frequently enough. Size queens may also be considerably less reluctant, perhaps even eager, depending on your size and their proclivities.