Supervised loans, not made pursuant to a revolving loan account, in which the principal is One Thousand Dollars ($1,000.00) or less and the rate of the loan finance charge calculated according to the actuarial method exceeds eighteen percent (18%) on the unpaid balances of the principal, shall be scheduled to be payable in substantially equal installments at equal periodic intervals except to the extent that the schedule of payments is adjusted to the seasonal or irregular income of the debtor; and
Okla. Stat. tit. 14A, § 3-511