[rabbitsncavyluv]

That isn't recommended. Please see http://www.guineapigcages.com/types.htm and scroll down.

Please don't use tubs and bins. They are just too small. The "large under-bed storage container" are usually barely 2/3 of the minimum 2 x 3 grid space. The largest containers readily available are commonly 6 square feet or less (80% of the minimum required at best). It only takes a little more effort to increase the real space your cavies have to run laps and explore. Don't settle for less just because it's convenient for you. Inches matter.

Just increasing the space from 6 to 7 1/2 square feet is a 25% increase for your guinea pig! A foot and a half may not seem like much to you, but if someone gave you a 25% increase in the total living space in your home, you'd be thrilled, especially if you were living in a tiny studio apartment! And if it doesn't seem like much, why not give it to them?

If you must use the bins, then you should have two, side by side, with at least an 8" wide section cut down from each adjoining side, creating a "gate" for them to walk and run through. Don't leave it so that they have to leap over the sides or climb over steps or ramps. (And it will take you more time and effort to cut it down, than make the Coroplast bottom. We know, we've done it. And it's messier to clean.)