RE: .049 Multi Engine Plane
Yes, it should work fine. Keep it light, place the engines close together as possible with out-thrust in both and use a large-ish vertical stab. This will help with assymetrical thrust when 1 engine runs out of fuel before the other.
If you're using Cox integral tank engines, you could drill a hole in the tanks, run a fuel line out to external tanks with fixed pick-ups. When you've flown long enough, roll inverted, push down elevator gently and both engines will starve and die at almost the same time....roll back upright and glide back in for a landing.