[Chaos]

I believe that while relative giants are a thing, anything that gets roughly around the point Sly mentioned (under 2ft or over 9ft) would have to convince an unamused GM.

However, I also believe that Liches are the only race that can be extreme in their size and get away with it. It's entirely possible to bind to something rather small (see: Demilich) or something quite large (though you're gonna have one hell of a time getting such a form). Of course, I also expect people to not have their forms bound to a small coin nor a titanic statue, so to speak.