The one thing no one has mentioned. From the way you're decribing this, you've programmed the flaps when "up" to be above the trailing edge of the wing. That's not flaperons, that's spoilerons! And will bleed OFF lift causing the plane to sink dramatically.

When we talk about the flaps being "up", we are referring to what you're calling "neutral"! Flaps NEVER go above the trailing edge of the wing.

The three positions you want would be around "neutral", 15% down, then 30% down.
Dennis-