RE: single or double wing foamy?
I'm a huge biplane fan. I have many ultimates. I think the biplanes are much more stable in the air than monowing designs. Also with a shorter tail, it seems as if they can pull much tighter loops. The knife-edge is also far superior to monowing designs in my opinion. The cabane's act like wings during knife-edge flight resulting in tail up knife-edge instead of tail-down dragging knife-edge like the monowing designs.
Plus, seeing a biplane roll, looks much cooler than monowing designs. There is just something about seeing those two wings rotating in sync.