don't know if we're prepared to accept your apologies Bernard

Sure, p of p is the real thing, and doubtless easy to obtain still - I did the same with it using those moulds when mine were young, and we made Disney characters, but I regret that the moulds have long since gone. I personally wouldn't have a problem using the modern equivalent - it isn't a question of ...oh well, no one is going to know, so I'll shove anything in ......... it's more a case of I have Polyfilla in the house already, and it's a more than adequate substitute, and unlike p of p doesn't 'go hard' suddenly - I'm sure William Morris would have gladly jumped at the chance of using a router or cordless drill had they been available in the 1880's.
Don't tell your buyers that you've been tinkering too much with these flutes, they might wonder what else is amiss

- best of luck with the mould making.