RE: My plane experiences snaking
Another very easy and simple way to test for a fix is to use card stock and masking tape. Fold some card stock and tape it to the rudder to increase the vertical fin area however much you feel should work. Fly and decided. The same technique can be used to make the rudder larger if you feel that's a better solution. You get greater rudder authority along with better stability.
It's easy to undo if it isn't the solution. It's easy to do again larger if it helps but isn't quite enough.