How creative! I've been trying to think of a cheap idea to build a little upper level loft, and this is a great idea. Is it secure, though? And is the plastic sharp where you cut it?
I have just made the exact same thing! lilouisianagal - mine is very stable with my 3 boars in it and I cut mine with a HOT! bread knife but my frined used a jigsaw. love4piggers - mine is quite secure with 3 bricks in it (I tested it before i let my piggies use it) and when I cut my box all I did was file the bits down but still got a bit worried so but a bit of heavy duty tape around the opening my pigs love mine and sometimes i put 1 plate of veggies downstairs and about 1 leaf of romaine/cos lettuce in the box so they get exercise going up and down the ramp it is really worth doing.