M_Boats: Stern Rail for M 17

I want to install a stern rail om my M 17. Railmakers, who did the pulpits for the M's, is here in Costa Mesa and were getting ready to send one off to an M 15 owner. They let me size that one to my M 17. I have attached a couple of photos. The M 15 stern rail seems to be shy about 8" from being the correct width for the M 17. My question is this....does anyone know the exact specifications of the cockpit of the M 17 (specifically that area where the stern rail would mount) ? Railmakers does not have that info for the M 17. Thank you.... Tim Brown Hull #254