Collision problems after rescaling my player avatar?!

Hi guys,

I recently had to rescale my whole player avatar, because I'm working with the Oculus Rift and I needed to have the player avatar arms 1:1 to real players arms. Now after I have rebuild the whole setup and made it about 4 times smaller I have a much worse collision detection. (My gaming world has an own mesh collider (no terrain collider)).

Is there in Unity something like an unvisible collision resolution that is depending on the size (in meters) of the gameobjects? Or do somebody has another hint for me?