Gator;
I am by far not an expert, so keep that in mind.
The P-38 can do some pretty slow manuvers, especially looping. For some of my loops the IAS may drop to 30-60mph easing over the top. At these times I might drop up to 3 notches of flaps. The trick is to stay wings level.
The P-38 will often then do a pretty rapid down pitch right after topping out. Basically I believe stalling, but then falling nose down. I get the flaps off before my airspeed gets back above 200mph.
You can also start loops at slower speeds than most other planes. Use a notch as you get about vertical. Then use 2 or 3 notches to get over the top using very light stick back pressure.
You can really stretch every bit of E out of these turns and many times watch planes shooting at you that just quite can't get their nose up to you.
Although it might also help to get slightly out of the shooters plane of flight. Do this with a couple of rudder kicks / small ail rolls while zooming and while going vertical.
BTW this never works on Torque.
IMO flaps are not yet modeled to their full potential yet, especially for the P-38. Practice these manuvers anyway to become proficient at them and be ready when the flaps get completed.
Best of Luck!
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Mino
The Wrecking Crew