For what it's worth, there's IIRC a very similar spell in Magi of hermes (the Flambeau who has Assume the Stature of the Giants of Eld, so that must be around p49), although I can't recall any details about it.
(Wrong thread, I wanted to read about your familiar and wound up here, stumbled on that. And I wonder how I did it, since they're so far appart. Must have thought about ALEXEI's familiar)