Well, the line between stall buffet and full departure is razor thin. If you are not smooth on the controls, the P-39s can be ugly spin monsters.
Rear vision is odd, I set my view at all the way back and slightly left.
Speed is pretty good for the P-39Q, faster than the P-38J/L between 10k and 14k. Climb is adequate, but not what I would call good. Since the flaps were adjusted, the Q can turn reasonably small circles. Turn rate is not great though. Acceleration is also adequate, being a little better than the P-51B. Like the 109s, the P-39Q (and D) will not roll right at high angles of attack, especially with flaps out. Rudder use doesn't help much.
I recommend the two MG/37mm package in the Q as it is a good trade-off for better speed, climb and acceleration.
On a whole, the P-39Q is a pretty good mid-war fighter.
The P-39D offers much less performance. It weighs more and is down 270 hp to the Q model. There is no WEP power either. Climb is poor, as is acceleration. The lack of power and added weight results in a larger sustained turn radius.
Take the 37mm and practice with it. One hit will kill any fighter.
Both accelerate well in a dive, and display good control at very high speed. E retention is very good for both, with the Q being the better of the two.
Bomb or drop tank shackles will cut speed by about 7 mph, as will the under-wing .50 cal MGs available for the Q model.
My regards,
Widewing