slowrotor,
Wow!
There is a lot of information on the Web about his engines, and it is very impressive. Not only did he invent the V8 engine, he also used direct fuel injection. Of specific interest to aircraft is the statement
"Its power-to-weight ratio was not surpassed for 25 years."
Mart,
Perhaps unfortunately, it not a simple spreadsheet. The algorithms are from pages 69-72 of Prouty's main book. These algorithms, plus more, were incorporated into a large Microsoft Access database and linked to many tables. I have previously looked at pulling a copy of it out of the database, however I never did because it would take many days of work.
I'm not ready to accept Leishman's 0.5 FoM. In addition, this FoM sits on top of the simplistic Momentum Theory (Actuator Disk).
You mention;
"The ideal blade taper planform for hover has chord inversely proportional to radius, which these aren't."
True but, this is the remark from Prouty, page 649. He is talking about aerodynamic performance in hover and vertical climb.
"(Some preliminary studies indicate that perhaps inverse taper holds some promise in this regard.)"
Dave