Bruce,
I just won one of your auctions on a lower grade book and I think that you should drop the "CGC guarantee" thing all together and just offer a "Satisfaction guarantee". There's no way I'm going to send the book I won from you into CGC, but what if I just don't agree with you on the grade? Will you take it back and send me a refund? (These are rhetorical questions, I wont want my money back, I just bought it because it has a cool cover and at the price I wouldn't complaine anyway.)
I'd feel better about bidding on an auction that has a "Satisfaction guarantee" then your current "CGC guarantee".