WW did you have a chance to compare the FM-2 flaps ?
I did... Didn't seem to have excessive drag with full flaps. It did require a slightly greater dive angle than the P-40, and roughly the same as the P-39Q. However, the FM-2 has a much greater flat plate area, so that would be expected in a shallow power-off dive.
Here's the comparison data.
Drag Coefficient:
P-39: .0217
P-40: .0242
FM-2: .0253
Let's look at wing area:
P-39: 213.2 sq/ft
P-49: 236.0 sq/ft
FM-2: 260.0 sq/ft
Let's look at flat plate area:
P-39: 4.63 sq/ft
P-40: 5.71 sq/ft
FM-2: 6.58 sq/ft
Let's examine the flaps of the two fighters. I'll provide flap area and full down angle. All use simple split flaps.
P-39: 26.2 sq/ft @ 43 degrees
P-40: 33.1 sq/ft @ 45 degrees
FM-2: 27.7 sq/ft @ 43 degrees
My regards,
Widewing