I have been flying the exact setup you mention for the last two years. The OS 300 twin is a great match for the GP Eagle.
I also have a homemade smoke system added that really spices up the flights. If I remember correctly, all up weight is 20 lbs. Including smoke system and onboard glow. ( I'm using a 4000mah NiCad for onboard glow). Running a 20 x 8 Zinger prop. I don't believe you can go wrong with this setup. I am using Futaba 3010 servos on everything except throttle.
Trust me. You will like it.

Shepp