>However, I think that if a 5 foot tall storm giant or a 6 foot
>tall gnome walked into the room you'd realize it without going
>through a more vigorous visual process (See "con).

I'd settle for a room echo when the spell wears off.

Sonso suddenly changes in size, becoming larger/smaller!

You might not actually know if they were their normal size
before, but you could see changes in relative size.