Unfortunately those pet store cages are never near big enough for one piggie, let alone two. I impulse bought my pig Pansy, and I got her the carefresh happy habitat because it was on sale at petsmart, and it was okay until my mom decided to get Pansy a buddy (best decision ever, in the end) and then it was far too small. It was about the same size as the cage you have shown here. I ended up making my own C&C and lemme tell you, I'll never go back. They LOVE their new cage. They have so much more space to run and just be pigs. So, I would highly recommend just doing a c and c, and perhaps you could throw the store cage in as a kitchen or something. I've seen people take sides off those cages and connect them to their grid cages. And as for the second level, when it comes to pigs, you should expand outward, not upward. They need at least 7.5 sq ft of ground level, uninterrupted running space. You could still make a loft, but it won't count towards the square footage. For having a pair, that would be the recommended size for two females anyway. If you get males you will definitely need to go larger.