*waves at the other Fancy Rats members* just found this place! I thought the Internet was meant to be huge, how come I've come across you two in two different places?
Furrynavel, someone on Fancy Rats put a Critter 1 on top of a Critter 3, you could probably put your Critter 1 on top of a Critter 1, just get some pliers on those ring things that attach the ceiling, only trouble would be access =/ could make a door! Two Critters side by side would take up more floor space thats all.
I never even thought to move my hammy into my spare Critter 2, shes happy enough where she is I think. Have a look on ebay Furryfeet, theres always cages on there. I'm thinking of buying a second cage and attaching them together as my hamster cage is tall rather than wide.