C&C Building a C&C cage?

I want to build a C&C cage for my female guinea pig and her new future friend. She is currently in a 35.5" x 15" cage. I think that that is too small and Im sure that many will agree. However, my Dad says that she's fine how she is and that we don't need any more things in our patio. But, I plan to put the cage ontop of a table, where I currently have more guinea pig supplies, and then put the supplies underneath the table (there's nothing underneath the table. I'm not going to be taking up anymore space by making a C&C cage.
That's his only objection.