I put out 6 of the Porcupine structures two weeks ago in Lake Thunderbird, OK. Have not been back yet to check out if fish have moved in. But will tell anyone who buys them that if your PVC is longer than two feet you need to drill through the lip where they are glued together in about three places and put a bold and nut. No. 8 machine screw will do the trick. They start to crack apart and the PVC will not stay in if you don't beacuse the longer PVC put pressure on the globe part. I built some for deep water with 5 footers in each hole and it was a chore getting time overboard without hitting the gunnels when you let them go.
Next one's I build will be out of 4'' to 5' old rubber or plastic hose stuck down in a concrete base about about the size of the small bags you can buy, that way no extra weight required and the hose is cheap. I even have some old soaker hose that would be good as it is rough like the bark on a tree. Good luck with yours.