without knowing maker of dagger, are grip eagle emblems interchangeable between SA and SS daggers?

Yes, the style is the same.

Problems is, many examples of eagles (when A-B'd) are not dimensionally similar, and most were hand fitted..so..sometimes your eagle will sit proud, and sometimes it swims in the recess.

Correct.

That is also why there are slight chips around the wings on some daggers, particularly SS. The space for the eagle was milled and two holes drilled for the prongs. The eagle was most probably squeezed in under pressure and between the slight tolerances for the milling and eagle, there was the occasional mismatch. Some grips probably split at the point.

Apart from the two holes and milled recess, this is only conjecture on my part.

Dave