What's t he secret to manage the JU87 or 109?

[Sauf]

Jimbop gets the essentials down pat here,

"Order of business IMHO: 1) ensure radiator is open to allow cooling; 2) learn how to trim the aircraft, especially rudder and elevator trim since most early fighters don't have aileron (a loose spring joystick helps here, cable ties are just great to reduce spring tension!); 3) keep an eye on the ball & slip indicator and trim with rudder to get true forward flight; 4) focus on prop pitch interactions with throttle to keep the boost pressure under control or risk the dreaded perforated water radiator."

Basically make sure your rads are open and try not to go over 2500rpm.