Hey Ron....Here's what I've found pertaining to my theory, and I'm emphasizing "theory", as it's definately not proven.
On page 43 of your 9C manual it's dealing with 2 types of fail-safe modes, one being standard, the other being what I was thinking could be the cause, and that's the "battery fail-safe".
Now....it's stating in there that the battery f/s mode is triggered when the flight-pack reads 3.8 volts or lower, and as I stated your plane will go to idle, or the value that you set it for. It also states if "nor" is set it will go to throttle total down w/trim centered. I would imagine the 20% that was set there was default setting. Think about this though, when you loose power, does it seem to go to low throttle, or fast idle, or about 20%?
What you might want to do is see if you can simulate the flight conditions without actually going to the air. Tie the plane up, have a buddy get behind it to stabalize, and run it like you are flying, and see if you can simulate, and recreate what your experincing in the air. Take voltage readings before, and about every 10 min or so, this might not be necessary, but you have it there on the ground anyways, and at least you'd know. This still might not tell you though, as the forces created by the moving airframe are extreme, and probably can't come close on the ground, but it may be worth a try, for your research.
Aside from that, take all your packs and give them a good cycle or 2, or even 3, and get some definate readings on the true capacity/voltage.
I've also copied a link here to the online manual section for Futaba's 9C, and there's a section to download supplements/technical updates.
http://www.futaba-rc.com/faq/faq-9c-q581.html
I really hope you get this worked out soon, this is one of the toughy's it seems. I've heard the 102 is an awesome engine. I own the BME50, and heard nothing but good about all of them. They are one awesome aerobatic engine.
I'm very interested to know now exactly what it could be....hmm....
I'm definately not any sort of authority on what you have going, but glad to share what I can.
