I checked with two CMs on two different days at the Member Accounting Dept. Both had the same answer regarding extra principal payments. If paying by check, so long as you include your contract number and the notation "Principal Payment" on the check, and you mail it to the address I provided above, it will be applied toward the principle. Also, the check should be made out to "The Disney Vacation Club"(not Disney Vacation Developement). As I stated before, I include a cover letter with the check with all of the details just in case.