Yes; we have.

The P51-D bubble canopy actually afforded a poorer rear and forward down view than the P51B with a Malcom Hood. The Malcom Hood, a british mod; was also evaluated here in the US; and since it too suffered from the NIH syndrome; the folks at North American Aviation opted for a bubble canopy. This is documented; and yes it is contrary to the POPULAR belief that you could not see your six from the cockpit of a bird-cage canopied plane.
The Jug with with an optimum head position adjustment actually has a better six view than the Pony in the sim.. so; why pick on my pony??
However; just as you can with a F4U, the sim allows head movement, turning this gripe into a non issue.. and I await the P51B with the Malcom Hood.

I'd sure like to get a snap view key that allows a brief 'head-down' peek at the lower guages in the Jug.. using page-down is very very clumsy.
Hang