Home-made PVC chastity tube

I started to wear my CB-3000 again but I find it too big for me. When limp, I only fill 60% of the tube, and when erected I can get a nice semi-erection. I would like to reduce my erections to the minimum. The optimal solution would be a device that allows no growth from the limp state. I thought of buying a CB-6000s, but before that I would like to build a home-made plastic tube. It would be much cheaper. I found a very nice device at http://www.tpe.com/~altarboy/nt000418.htm:

I will try to construct a similar one with a small tube of 1 inch diameter.