I was also wondering if you made any progress with this. I am trying to construct a wet neck setup for my skimmer (an 5 year old ETSS downdraft). I used an acrylic tube with an o-ring seal to the outside of the skimmer neck (in the collection cup) and a roof that has a hole in the inside that is the same diameter as the inside of the neck. It isn't working too well. It doesn't make a nice sheet of water. I'm bleeding the water for it off of the feed for the skimmer and I'm only using one 1/4" line so it might not be enough flow. I think I'm going to see about increasing the flow a little. Does anyone have any other ideas about how to induce a nice laminar flow?
Now that I think about the volume of water involved to cover the whole inside of the tube, it seems like it would take more than you could fit in a 1/4 tube at a reasonable pressure...
I've attached some pictures of my setup...