Why no Hispanos over 10k? I did a quick web search here on my phone and failed to find any information on this statement.
You can watch Hispano's cover of SpitV,
But ,F4U-1C's don't have such cover.
Yes,F4U-1C don't have anti iced cover for Hispano.
Hispanos of F4U-1C were iced on over 10000ft.
you can read such situation on "Corsair Aces of World WarII",too.
It Book is series of "Osprey Aircraft of the Ace".
(But I have it of Japanese Edition.)
USN used Hispano for aircraft normally,when they got F8F-1B.
May be, SpitVs on Port darwin were same situation when they fought against Zero.
because, G4M1 didn't get big hole on Port darwin,and many of them could return to base.
But this reason is weather of Australia, I think.