Greetings. I've had my two cavies for a week now. One is really tiny and looks about a month old, the other is probably two months. I bought a marchiaro tommy k 102 cage. I am looking to expand the cage as my boyfriend is interested in getting a third cavy/and even if we don't I'd like to expand it. I'm interested in either a second floor to it/ramps etc. I've been browsing all of the amazing cage pictures you all have but would like your input and definitely the materials you've used to expand your cages. Again, I'd like to add another level etc.
You could use the petstore cage as an upper level, that is what I am doing right now. I am remodeling one of my piggies cages and I wanted to incorporate the petstore cage in the c&c cage. This is a picture of some one elses pet store cage incorporated into their c&c cage.
https://www.guineapigcages.com/gallery/515/
https://www.guineapigcages.com/gallery/516/
I would not add a second level in the pet store cage. You asked about building a ramp that was two feet high into the petstore cage, you could always drill a hole in the side like in the 2nd pic. and keep the peice you drilled out so if you went to the vet/vacation just tape it back on.