Thank you again for the kind words!
colorex: To balance it is a breeze, the belly has a step to help it take off from water, the CG is right on that step. It balances well with the two batteries I have tried, one 1300 and the other 1000 mAh. I'm waiting for a bigger battery, around 2200 mAh to extend the flight times which is about 4-5 min / battery now. To check for balance is also easy, just set it down and see if the center is right on the step.
anas: The motor I'm using is a Turnigy 2826 - 2200kv from HobbyKing. At around 340 watts and about 1000g of thrust for a 600g bird, I think I have plenty of power. Most of the flight was at about 40% throttle to save the battery and the couple of slow takeoffs at half the throttle.