If you are flying a twin, you may want a second 15 size plane (I'm thinking cheap ARTF).

Why? so that you can run in each engine well before putting it in your twin. Ideally it should have the same mounting position so that you can tune it for that.

This way any reliability issues can be sorted out before risking your nice plan built plane. Most twins (as you probably are aware) can be a nightmare to fly with one engine dead.