Your problem in the P40's is with the maximum size ring the N2/N3 used.
70Mil ring and dot.
I have a current package of historic gunsights in 100Mil main rings including an N3/L3 70Mil that fits the P40's, P39's and P38's. All are in 512x512 1mil=2pixel.
I've worked up three Japanese graticule the Type98-120Mil(all A6M), Type3 - 100Mil(Ki61/84) and Type4 - 120Mil (N1K2J).
I've combined the Navy Mk8 and AAF N9 into a Mk9 to take advantage of both as a custom sight along with a Jabo version of the Revi16b to use with the rockets in the Fw190F. PB1 trajectory was the same as the Mk108 tator.
Since HTC includes the 6star 100Mil K14 I have included the K14's 100Mil ring and center cross. Other than that I have all the Historic graticule AAF, RAF, Germenay, Italy, Japan, Finland. With Saxman's permission I include his 100Mil MkVIII.
Whats a good free file sharing host?