Rafe,
I think you got it.
The F2G had a 14' diameter prop.
The F4U started with a 13'4" prop that was changed in balde design to reduce prop tip speeds in 1944 to a 13'1" blade 6501-A.
The larger the prop and higher the rpm the less efficient that prop would be over say 20,000FT. The F4U had to reduce to normal power at that alt in climbs for max climb rate without overheating. In level flight it was not as important.
BTW Rafe do you still want that -5 stuff? Send me your email again.