Some interesting (and strange!) stuff there Colin, thanks.
Back in the '80's, one of the BBMF Hurricanes flew with a 4 bladed prop, and I think a Merlin 66. The 'Flight's pilots told me that the performance increase from the prop alone was marked, and wondered what it would have been like, and what difference, if any, it would have made during the BoB.
Their words, not mine, and I hope this doesn't spark off another debate somewhere!!!