I would recommend fixing the problem at it's core instead of trying to scale inside C2. By that I mean making the sprites the right size before you import them, it makes the whole process a lot easier.
Now, obviously, your solution should also work, I'm just saying this is how I'd prefer to do it.
This way, if you want to change the animation at some point, all you have to do is make sure the frames are the same size and it should work straight away without having to create new sprite objects and position/scale them.
I've corrected the last example so that the hinges are the same size, but I've just scaled the sprite up, so expect some loss of image quality.