By the way, I elevated the 7714 shield today to 20 feet on an eave mount above my garage (by about 6-7ft). I know, that's not a good comparison to a shield at 5ft, but wouldn't you know it, after that, it ran neck and neck with my FARS (inside the specs for the 31s).
Admittedly today was a mostly cloudy day. Previously, though, during cloudy periods when the passive shield was closer to the ground, it ran warm by at least a degree (if not two) during the day which made no sense other than bad siting. When the sun made an occasional appearance today, both shields ran extremely close with the new arrangement.
Thing is, I don't have a good spot for another shield at 5ft AGL without compromising my main station, which I'm not going to do.
Even though it's not technically a valid test, I will report results once sunnier conditions arrive (maybe tomorrow but more likely Thursday). This may be a decent workaround solution for people with limited siting options and/or a sheltered yard who don't want to bother with a FARS.