Hello Frozen,
The commercial aircraft you have seen the wing tip plates on have swept back wings, leading edges. This promotes spanwise flow toward the wingtip and hence fences and tip plates help reduce the losses. It all started from the swept back leading edge. Sweep the wing forward slightly, 5 degrees or so, and the spanwise flow is gone. Also the foil will not ventilate, pump air down the leading edge, at high speeds. This is the best solution to maximise the span effectiveness of an airfoil. Check out a high performance glider with slightly swept forward wings.
Bill