Credit Card Security Settings ..

What does everyone do in regards to their security settings? I've noticed that I get as many declines as I do sales in my shopping cart. In last few days I've had messages sent through customer service from potential customers complaining that they have great credit and blah, blah, blah ...
Right now I have it set ... for lack of a better term, on medium ... or whatever label the merchant company puts on it. Here is the kicker though, most of my declines show the security code on the back of the Credit card doesn't match. I'm thinking of taking that option out, I mean ... if a customer puts in all their info., name, address, email, selects product, phone number, cc info, fingerprint, dna, etc. !!! and then clicks the process the order button, do I really need their honk'n security code on the back of their credit card? Thoughts?

Also, does anyone have a recommendation for going after the customers that declined out? Or customers that filled out their information and never hit the final buy button? Does anyone have standard emails that you send? ... and if so, how well do they work?

Thanks in advance to the superfreak-a-delic Warrior World !!!