Forgive me @Cornish man, but you have spiked my interest even further, by your last post, on how to preserve a rare breed. I have a question if you wouldn't mind considering.
Why cull hard? Surely any breed will show variability and, if you are reasonably content about the purity of your stock, I cannot but wonder whether hard culls will ultimately end up with too much in-breeding and weakening of the breed !?
I do not mean to challenge your strategy: I'm just trying to understand rare-breed recovery strategies and would be most grateful for further explanation.