The way F3A schedules have evolved, a triplane (and soon to be seen quadriplane with a twin cylinder gas engine up front) was inevitable. It is a straight forward way to minimize wing load. Consider the tripe has around 1500 squares and weighs 11 pounds. Loading is a scant 17 ounces per sq foot. Not quite foamy like but much closer. Also consider the quadriplane with it's 2200 square inch wing.....a wing load of 11 1/2 ounces per square foot. That's foamy territory
The dimensional limit up is 2 meters. The box is a 2 meter cube....unless FAI changes the rule (doubt that)
I think the idea of an X-wing has merit. Maybe not exactly an X format but rather Rhombic. Each wing set, each side, can be fashioned into a diamond or rhombus.
Should be simple to play with one made out of foam. The side area this concept introduces is greater than anything done to date. Should fly about the same in all attitudes with similar control input. If I had some foamy gear laying around I just might try it. BUT I don't so if anyone is so inclined, try the idea in a foamy and report in the K-Factor. Of here since this forum is more visible to the world