Tell her, dammit!
Man, I think you guys have the wrong idea. I see so many white guys try to set things up behind their wives backs, or say, "she can't know", or "how do I get her to do it?". Tell her! Be open with her. Talk to her about what you would like, or what you want. Sneaking around about it just makes her think you're sneaking around about something. Be genuine; be honest. Can so many married couples really not know what the other one wants or desires? Isn't marriage about sharing those innermost desires with one another? Can so many women be so rigid and vanilla that they would be horrified by the thought of their pussies getting stretched to their fullest by a huge black cock?? (As a woman, that sure sounds pretty damned good to me!!) I'm sure there's some women out there that just wouldn't... but I think it's less than you think. Any woman that enjoys sex at all has at least a chance of accepting the idea. If she sees how much it turns you on, chances are she'll be turned on, too. DC's member area has pretty good instructions on how to introduce your wife into the idea. I don't necessarily agree with EVERY step, but the general idea worked on me... and my husband never even read the instructions! He was just honest!