Thanks! Yeah... I'm trying to fix that bug (related again to JSONP), but wanted to post it here in the meantime. And planning to move from circles -> svg:paths with the next D3.js release (they've rewritten / fixed the geographic clipping functions).
just clipping the circles with the outer ring might help. when i did this - http://www.acooke.org/arms.html - i tried to make the ellipses the correct shape, but it's non-trivial for extended ellipses on a curved surface (although yours are small so perhaps that's not an issue). anyway, the big breakthrough in making it look natural was to simply clip at the edge of the globe.
