One thing that is indeed a pain is that you see very few photos of the underside of planes so It's hard to find examples of ideas you might want to try.

The black and white blocks you see like on the bottom of Extreme Flight planes would be hard to do without recovering. That's why I'm thinking strips is the way to go.

I've found with my electric sailplane that one 6" red stripe 3/4 of the way outboard on one wing is enough to maintain orientation with an all-white airplane. But, a sailplane always viewed from the bottom is a bit different than an aerobatic plane.