That looks like a cool tunnel. The only problem that springs to mind is that piggies have had damage to toes and nails from the strangest places, and if the tunnel can move around the way when they're in it, I would worry that there could be a painful foot accident if it rolled over whilst their foot was in a hole. If you were to steady the tunnel using bricks either side, I would feel less worried at the thought of an accident.
Edit: Are the holes big enough? I'm such a worry wart!
I drilled the holes in myself (they are only 2 1/2 inches as this one belongs to the gliders, the holes would be alot bigger for the piggies)but it doesnt have to have holes so I could leave it just as a tunnel....thanks for the advise JarBax as I wouldnt of thought of that.
People use drainage tubes all the time for tunnels. This looks simular but smooth. I would be afraid to drill holes for a little foot might get stuck. You could cut it into sections and I bet they would hang out in the tubes.Pigs love getting in things. The one questions I would ask is how big are your pigs in relation to how large the tube is, you don't want anyone getting stuck. All of my hidey houses are plastic so I know that is ok.