I created 2 exact same loans - declining balance, 10 installments, 5% interest, 100 principal. Only difference is one is designated as a variable installment loan, and the other was not.
See Kenna James on the demo server for the 2 loans, currently pending approval.
Variable Installment loan account # - 000100000000978
Non-Variable # - 000100000000977
The schedules are the same, except the last installment. In the variable loan installment loan, the last installment does not have interest.