I'd never have enough time to enter the OAT value manually as the only possible way I'd ever get a high enough airspeed to worry about "ram temperature rise" is in a full power, pure vertical dive... after the wings have broken off!
Many of these systems are being installed in RVs, which could have ram temperature rise of around 3 deg C at typical cruise speeds. I agree that this size error would only have a small effect on the calculated TAS (and hence the calculated wind). I simply raised it as one example of the many possible errors that are not being accounted for, as a counterpoint to Dynon's apparent concern about the possible errors associated with pilot-entered OAT.
Besides, without extensive wind tunnel testing, how the heck are you going to know what the "ram temperature rise" is going to be for a given probe location?
Actually, all you need to do is fly at max speed at constant altitude, wait until the indicated OAT stabilizes, then record indicated OAT, IAS and altitude. Slow to minimum possible speed at the same altitude, let the indicated OAT stabilize, and record the data again. Do this on a few different flights, so you have a bunch of data. Take the data from each flight and plot indicated OAT vs (TAS squared)/7592 (this assumes OAT is in deg C, and TAS in kt). The slope of the line from each flight is the probe's recovery factor. Average the calculated recovery factors from several flights.
I'm no expert on mach-number aerodynamics but I agree with Dynon that I'd be far more likely to introduce errors by manually entering (and "correcting") OAT values.
The pilot would need to make a 30 deg C error in his entry to have the same effect as the already existing errors that some aircraft have on their static source. Yet Dynon is apparently worried about the effect of OAT error, but not about providing a way to correct the much larger, and much more important possible static source error. Go figure.
But I do have to hand it to you Kevin. You, by far, have the most elaborate excuse for not spending $65 that I've ever heard.
I'd purchase the OAT probe if I wanted the wind indication. But it isn't important enough to me to justify running more wires from the wing to the instrument panel.
I am much more interested in eventually having a way to correct for static source position error, before the static pressure is used to calculate CAS and pressure altitude. But, I recognize that not one in a hundred customers is interested in this feature, so it won't happen.