Transparents on top and opaques on the bottom. I used to be able to see yellows at up to two miles but I would bet I would have trouble today.
Ahh, maybe that would work.
I can't use transparent film though, because I think it looks goofy. Isn't transparent film on top or bottom kind of pointless though, if you have opaque on the other? The net effect is opaque, isn't it? Is it just the difference in color that helps with visibility?
I know when I started out in RC back in the 80's, I used to make an effort to cover my planes with opposing colors (light bottom vs dark or bright top, etc) to help with being able to tell top from bottom, left from right, etc. At some point I moved past that, and found I didn't need to do that to know what my plane was doing. I've crashed a lot of planes, but never due to visibility/orientation problems.
I had an aerobatic biplane I covered in yellow, but it's been so long ago I don't remember much about how far out I could see it. It was a tiny little plane (3' wingspan, .25 motor), and I was never flying it with distance from me or high alt as a goal though.
One problem I've noticed though is that I find myself "watching" the plane, rather than "flying" it. I'm so used to watching my birds fly that I almost expect it to handle things on its own, lol!