What a cool idea. Actually I think anything with a bubble canopy tends to become much sleeker and doubtless it would have increased the speed of the Hellcat by a small margin too thanks to the reduced drag.
Actually the bubble canopy increases
the drag slightly; that's why the "razorback" designs stuck around for as long as they did and even stuck around at all (and why later supersonic designs like the F-4 and F-102 dropped all-round visibility), it provides smoother airflow over the fuselage. But at that time all-around visibility was considered more important than the almost negligible increase in drag, and more powerful engines more than made up for it anyway.