RE: need help configuring an airplane for electric flight.
Raul,
Hi, well first off I'd reccomend you getting access to a calc program like MotoCalc or one of the others out there. Will allow you to play with different combos of props/motors/ esc's/ batteries/ and airframes.
But anyhow. As it's a 46 class, you could look at name brand motors like EFlite, they now classify their motors by size. Or look at stuff like HTX from China, normally half to 1/3 the price of the name brands, and they are really good motors.
Let me get ahold of my bud Ken, aka "blisters" , he's a whizz at this kind of stuff, and can probably rattle off everything you'll need, off the top of his head.
As for the 123's, all I can tell you is what I've seen. I had a friend who had the Hangar9 Mustang (similar size to yours) powered by them, and I don't think he got more then 5 min out of his packs.
And I didn't like at all the cut off. At least on his, there was really no warning, like a lipo gives, on his the prop just stopped. Many, many dead stick landings.
But that's just my view.
One last thing, on my stuff, If it calls for a 46 I tend to jump it up one size, like to a 60.
I look at it as the motor doesn't have to work as hard to fly the plane, and you always have that little bit extra, just in case.