I have the same problem, but need a different solution. I'm working with an OPM CSA 1099-R and an OPM CSF 1099-R. Neither one has more than 13 boxes, which becomes a problem after box 9b. If I use the default boxes on TurboTax's form to enter state tax withheld and the state/payer's state number, TurboTax flags an error and wants me to fill in yet other boxes that don't exist. So, it's not just a 1099-R, but I don't know how to adapt the form. I don't recall having this problem in past years.
