Hey Dude - I dragged my feet getting back to you (life happens), but here you go
I tried it in hard mode, and again I loved flying it. By chance, I went up against the P-51D-30 (not the AvHistory FM), and it was like taking candy from a baby. That's great, but it's "too easy." The Mustang is the natural enemy of the 205. They should be about even in most respects with a slight advantage to the MC.205. It should be a real struggle for the 205 to defeat the Mustang, but as the player against the AI, you should (just barely) prevail.
So it happens, that I made an FM for SF2 for this plane a long time ago. I wanted something else for the TW Mustang to shoot at. So I compared our two FMs. The major differences between yours and mine are here
[LeftWing] / [RightWing]
Yours:
CL0=0.1006
CLa=1.3474
Mine:
CL0=0.0112
CLa=1.085
Next section:
[LeftOuterWing] / [RightOuterWing]
Yours:
CL0=0.0330
CLa=1.1675
Mine:
CL0=0.0115
CLa=1.575
So your FM gets TONS more lift at 0 AoA (CL0). Any increase in speed and you'll get more lift, LOTS of it. If you pitch up (CLa), you still get LOTS more lift than I do. This means you lose very little speed in the combat turn, which means you can sustain the turn better than anyone. When I landed I tried to "spill air" to lose speed and altitude, but I couldn't because any nose-down attitude increases speed, and thus, more lift. I got it down, but I missed the airfield by about a mile.
Take all this with a grain of salt. It's only an opinion. If you're happy with it, run with it. I certainly do with my FM mods.
My rule of thumb is: Fly with the new FM. Once you're happy with it, switch to the other side and fly for it's enemy. Does it still seem reasonable? Does it match historical precedents? Is your a6m2 out-diving your P-40? If so, and the historical P-40's only real effective escape from the a6m2 was diving away, well something isn't right. Back to the drawing board. And I swear, I DO go back...for hours on end. *sigh*