Many years ago, a friend and I made some wing tip tests. He built a "sort of" wind tunnel and we used a stub wing mounted so we could change the angle. We had thread glued to the leading edge and wing tips that screwed on. We were mainly looking for the tip vortex. We did not have any measuring equipment and only observed the path of the thread as the angle increased.

The downward curved, Hoerner, wing tips and end plates were the best with straight back threads. Next best was a squared off tip like a UCD with the tip removed. Block wing tips were next, followed by the curved backward "Stick" or UCD type tipe. Worst were the round, 30's style tips.

Basically, we found that any tip was worse than no tip and the more rounded or curved you got, the more vortex you got causing the threads to wrap around the tip. The Hoerners look nice, but aren't practical for an arco plane that does inverted/outside moaeuvers. End plates were the best, but they can kill stalls, snaps and spins. You will land slower, but you'll need more elevator to get any stalling type maneuver.