I have travelled to over 500+ sites in my day, and have only seen 2 installations using interleaved bays (WXXI-FM Rochester, using a 6x2 Dielectric, and WPXY/WCMF using a 6x3 Shively) , and 2 with a dual input antenna (WBUF-FM using a 2 bay Shively, WKNE-FM using a 2 bay ERI).
Maybe there have been more, I am not familiar with other sites installations.
I've only been able to Monitor WKNE-FM in HD , and noticed that there are areas where the Analog is really almost non existant, but the HD signal is rock solid, and others where it is the exact oppisite. Thankfully the station's time allignment is perfect so when it does drop its not a big deal...
"To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be."