The 190D series could have a gun firing through the spinner because it was an inline (V actually) engine design. The 190A series did not because they were radials. I doubt there'd be room on top of the engine for 20mms though, they had large blisters up there just to fit the 12.99 mm MGs. But the D13 did not have those cowl mounted MGs.
I am looking forward to recreating the yellow-10 skin once the template for the 190s are updated to AH2 specs. The current skin IS 1024X1024 but from the dev updates I have read the AH2 format will not have any mirrored textures. The biggest problem with my skin is that the spinner should be bright green with white spiral (there's no way to modify this due to the AH1 template, note all the Doras have the same spinner), but the camo needs some work too.