Coastdowns have been a mainstay of recumbents for years. The problems with them are, you have to normalize weight and there's always a difference of opinion on the validity of the details - what speed to start, do you measure acceleration, top speed, total roll-out, etc. When adding fairings, the weight thing can be important. And I'm not sure how any of them would be turned into a magical CdA number. Measuring power at the hub would seem to be more reliable, but few non-racers are willing to buy a PowerTap hub or similar equipment. (I know a few are, but they don't talk about it.)
Even 'aerodynamic' TT uprights seem to get more benefit from drafting than a typical lowracer. That tells me something, even without knowing numbers. I've been in a 5-bike lowracer paceline and the benefit is barely noticeable - certainly not the kind of help it gives the uprights.