That is pretty damn sweet! And Im sure it cost allot less than the Ikelite one...
Well... I bought 50cm of pipe (enough for 5 shades ar least), and bolts and protectors for another 5. It all added to less that 20€ (less that $30 today). So, it's about $6 per shade. Yes, it's less that the original one... 
So what size is that pipe?
It has an internal diameter of about 23cm - 9", but it ought to be 21,8cm - 8,5" to better fit the 8" dome. Anyway, it works, although perhaps the space between the shade and the dome does not look so nice.
In fact, after having built the shade, I've been told that it's not adequate for a 10mm FE like the Tokina one (because of vignetting), which I have ordered. I would have felt a bit stupid buying the shade and then leaving it at home. Now, if vignetting occurs, I can build a new one for the FE. In fact, it takes me less than two hours to build it once I know the adequate dimensions.