This doesn't answer the OP's question, but may be of interest. I understand that if you were on PAS and retire at 55 then sign on for FTRS you may actually get paid more than you did in Regular Service. As an example, say you retire as a Sqn Ldr on PAS, and take a Flt Lt FTRS post, you will be paid as a Flt Lt, with your pension abated to reflect your Sqn Ldr PAS income, however, as you are no longer PAS, you will be paid flying pay on top of your income ~ approx another £10k per annum.
Unfortunately I wasn't PAS and so didn't pass Go and did not collect my extra!
Daf