Lumi running animation lines

Legs and arms move fine, tail bobs around nicely except in one frame, but her cheek, eye, and ears seem to grow and shrink (so does her hair, but to a lesser extent). I didn't want to just trace her head because it wouldn't look like it's moving, but now it's moving too much. Anybody got any tips to improve head motion in a running animation short of just practice or tracing it?

Kyte - The Pocket Foxbunny (If anybody is wondering why my comic is still late, it's because this is the first panel of the page. It'll probably look a lot better when finished though. With a moving background, and maybe shading.)