To pay off $128,000 in 5 years at 6.42% interest you would have to pay almost $30,000 a year ($29,996.08 if my calculations were right). Monthly payments would be $2499.68, so I suppose bimonthly would be $1,249.84. You did not say what your current payments are or if they are monthly, but you would have to specify that anything over your current payment would have to go to principal.