Dave,
I had a reread of Prouty Blade element theory with tip correction last night. I'm a bit confused because your spreadsheet looks like just momentum theory with the assumption of 0.7 FM. I don't understand how this proves Leishman's 0.5 FM wrong?
I'll overlook the Lycoming O-235 producing 105.2HP too.
Delta3,
I may not get the chance to read Leishman as thoroughly as he deserves this year, since i am supposed to be getting up to speed on differential geometry for my Physics final year project! I'll have the book on standby though so i can refer to any pages or equations you might reference.
That book Dave points out looks interesting too. Clearly X2 has already answered any concerns about speed limitations. It might be a useful engineer's guide for general performance calculations / parameters.