I was at a hardware store and saw a 4" PVC "Y" connector that I thought would make a nice tunnel. I had a Guinea Pig when I was a young lad, but I can't remeber how big they get. I plan on giving my son and daughter a cavy for their birthdays and am planning out the cage. I saw somwhere on this site that someone suggested the PVC, but they didn't say what size. Is 4" in diameter large enough? I'm worried about it getting stuck and not being able to cut the PVC.