------------ My feeling was the lift characteristics were linear mathematically and the characteristics of both airfoils would be available to some degree. (They would add up, so to speak, much like the properties of oil in a multi-grade variety ... or wave phenomena, etc.) I wanted a slightly positively stable plane that wouldnt croak upside down. ---------------

The stability of the airplane is a function of the CG location relative to the Neutral Point of the airplane and doesn't really have any thing to do with the airfoils. All you get with the mix is that at a certain negative angle of attack the top wing stops creating negative lift slightly before the top wing. There is not much to gain from not having both fully symmetrical in a model. Sometimes the mix isn't necessarily a beneficial thing to do.

In full size man and cargo carrying biplanes like the Beech Staggerbi that never do more than a loop and roll once in a long while then an airfoil optimized for upright cruising would be a better choice.

---------------- As for flying ... it barely flew on a 3:1 280 speed, 8 cells. It soared on a slope really well with no power. With a 4:1 speed 300, 8 cel, 8x6 prop it really flew well. When the speed dropped, the tip stalls were meaty. It was good that the recovery was pretty fast... -------------

It is pretty heavy for a speed 280. Fast recoveries are always welcome!