If I remember correctly, the T-1000 needs to transform into something in "its size" and need to use all its liquid metal. He can't transform into something small because of that and he can transform into something bigger if he can create holes in his shape but he cant transform into something ver big that need mor liquid metal then he have (wihout holes  )

If I remember correctly, the T-1000 needs to transform into something in "its size" and need to use all its liquid metal.

He can't transform into something small because of that and he can transform into something bigger if he can create holes in his shape but he can't transform into something very big that need more liquid metal then he have (without holes).