I fly RC twins & triples..... twins are a wonderful thing..... the sound is like music.

Like others have posted, the key is to keep your engines rpm as close as possible, ESPECIALLY with a P-38.
Twins also fight you a little bit in a turn.... they like to go straight.

Most crashes I have seen are when one engine fails and the pilot turns in to the "engine-out" side and the whole plane flips & crashes.
(stay away from the "dark side" Luke)

I just bought a "twin-sync" http://www.troybuiltmodels.com/items/WRCTWINSYNC.html and will install it in my H-9 B-25 & H-9 Twin Otter.

The Twin-Sync is supposed to keep the engines rpm's close together and drops to idle on the one remaining running engine if an engine goes out.... you then bring the throttle-stick back down & the running engine can then be throttled up. Watching twin RC crashes on You-Tube, by the time you realize one engine is dead.....it's too late.... especially if the field is noisy and the plane is down range a tad.

P-38 is my Dream-Twin..... but even after 5 years with twins I have not mustered up the courage to try one yet..... Good Luck Cowboy & have fun.... it's a wonderful hobby.