Also - just FYI ...
I have always had a set amount over my monthly payment taken out of my checking account - just call Member Accounting. You can specify how much "extra" you want deducted in a signed letter and fax it to them. They'll set it up for you, and make just "one" deduction - including the base payment and the extra to principal.
Recently - I started paying the majority of my bills online.
In addition to the extra that "they" are taking out, I've got a recurring payment going out bi-weekly (payday!).
The first time I set this up, I mistakenly addressed the payee as "Disney Vacation Club," and they applied it to my dues.
So make sure any checks you send, whether electronically or via snail mail, are payable to "Disney Vacation Development," and that your contract number, and "principal payment" are indicated on the check.
Hope this helps!