[Gnomasz]

I'd say the Postures Table doesn't have an "upside down" entry, so the player was right to expect there is no penalty (though it would be nice if he talked with you about it while creating the character).

I don't see a reason to require three points of contact that aren't described anywhere in the book.

Rules-wise, I'd say you might consider it Bad Footing for -2 (as movement along the ceiling costs more movement points), but also attacking from above target for +2, so it cancels out.

The ability costs a considerable amount of 18 points, in the same ballpark as Song of Terror, I'd say, and not much less than Turning. It should be powerful.