How do I build a double cage

[Sabrinasmommy]

Another member here suggested that instead of adopting out my male piggy that I build a cage for him ontop of the cage I already have. I figure I could just lay another C&C cage over the top, but how do I prevent it from sagging? Also, How would I rebuild the bottom cage so that I don't have to take it apart every 4 days to clean it? Is there a way I can make it so the tray slides out or something?
I also think that if I do build a double cage I will switch off of fleece since my cat will no longer be able to jump in it and I can use some other material and he won't be dragging it all over my house.
Any suggestions and/or directions will be greatly appreciated. I am so excited at the thought of not having to give up my piggie!