To add a little more to this discussion, I talked to several peole about the Funtana 40 and the consensus was the very wide, constant chord ailerons were the culprits. The feeling was that any small movement would greately affect the tip lift and had they been tapered, you wouldn't have the rock in harriers.

Here's another thought, from what I have seen in same size planes, .46-.61, the lower aspect ratio wings tend to harrier easier. The Pizza Box plane, PBF, and the Coroplast SPA3D will pop up into a harrier in a heartbeat. The PBF at 24x24 had an aspect ratio of 1:1 and the SPA3D has a 2:1, as I recall. The very low aspect ratio should have a very strong tip vortex. In addition, a large portion of the wing is covered with the prop blast compared to a high aspect ratio wing.

Finally, most 3D planes use a Vortec or similar airfoil with a straight line from the high point to the trailing edge instead of the usual curve. This is probably similar to, or a simplified version of, the double reflex airfoil which tries to break the laminar airflow into turbulent at the high point, increasing the lift and lowering the drag. The dimples on golf balls do the same thing.