Looks good - how efficient is it? I have stainless CFC but run through a pump and recirculate with a SS WIC also... but I am sure that copper is quicker. Yes?
With the caveat that there's a lot of hand-waving involved, I'd say it's ~2/3 as thermally efficient as a properly-sized plate chiller, but in a home brewing setting that means using maybe 11 gal of water to knock out a 5 gal batch, instead of 8 gal.
I ran a couple quick trials (they're below the actual build instructions) and for an "ale" knockout (wort outlet 12°C above water inlet) it ran a 2.3 ratio, about the same as the copper chiller. At least in theory, the longer the tubing is relative to its diameter, the less effect wall material/thickness will have on heat transfer. The all-stainless CFCs that are on the market (KegCo et al) use shorter runs of larger tubing, so this should be significantly more efficient.