Any question answered...

Well it'll probably reduce my CdA by about 0.001, at about 1/6th of the cost of a TriRig Omega which would give roughly the same saving, so I suppose I've just talked myself into buying one.

It's nowhere near long enough to generate any kind of saving, the flow won't attach to it, and the flow is both slow and filthy at that point just behind your elbows and just in front of your knees anyway. Save your money and get the Omega a month sooner, that has a proven benefit.