Only the F2G1 and F2G2 "super Corsairs" built by Good Year powered by P&W R4360's had the bubbly canopy and they never even saw service
got any documents to back that up?
I thought they even went as far as to replacing some of the birdcage canopys on the early F4U-1 models with bubble canopys  in the field as a field modification.... 
and used the bubble canopy on the F4U-4's & -5's  as well as having most F4U-1D's & -1C's with bubble canopys also.....  with some F4U-1A models thrown in as well 
is everyone talking about the same thing here?  bubble canopy  vs bubbily canopy ( is extra buldging bubble outwards )  vs the original birdcage
Saxman?    Widewing?  
TC