Well I flew the Mossie last night and made some notes:
The mossie has the ability to outturn the P38, but only in certain circumstances. The Mossie must have some E going into the turn first of all. Since there is engine torque, you must turn to the left for better results. Also, in the flat turns, you will notice a very unstable gun platform, and adding some rudder makes it much worse. In conclusion to this, the mossie is at a disadvantage due to the wallowing of the nose, and slow elevator response. Rudder response is also very very slow when going over 400 mph.
All that the P38 has to do is either turn to the right, or utilize the vertical. In this fashion, the Mossie will be like a shark on its belly- immobilized. With the P38 having no torque issue, and stable gun platform, it has the ability to flop right over and pounce on top of it. Also the 38 has awesome rudder respone (likely the best in game) and can change direction quickly with a little input. P38s will also be able to pull out of a stall without breaking a sweat. But for the Mossie, prepare to ride the joystick!
DieHard, I looked at those charts in the link that you gave me. While the information is fairly accurate, it can be misleading. I have found that just because the Mossie has a tighter turn radius does not mean that it is superior in a turn fight. P38s have better E retention in turn fights than the Mossie. So it will have an advantage.
To sum it up- dont get in a turn fight in a Mossie! Keep your E and learn to manage it. But if you do get in a sticky situation, be very careful with using rudder. Just like the Brits said "If you use too much rudder, the Mosquito will bite!"