Personally I don't like the sporran to hang below the family jewels or "goolies" as Arlen puts it

I see some very low hanging sporrans on some, especially on celebrities - David Tennant for example (Dr Who) and wonder if there is something Freudian in it.

But a sporran can actually look lower than it actually is depending if a belt is worn or not as our eyes judge from where one sees the kilt begin.

I was more under the impression that the "three finger rule" was more to do with the distance between the bottom of the kilt and the top of the hose.