I don't have an answer for this question, just a tip. I have found that the rear wood bows tend to flatten out over time, even with the metal reinforcing band attached. We just disassembled a 220 Cab A top and when the metal band was unscrewed from the wood, the metal returned to it former curved shape. I've noticed more than a few cars where you can see that the top is flat across that bow, even on restored cars.
Actually my trimmer (who is also a woodworker) could make that wood if you have the pieces, but I don't know when he could get to it.