[aerohead]

Ford published a -0.1825 pressure coefficient behind the tailgate.
Test conditions were:
117.333 ft/second
29.92-" Hg
14.7-psi
1500- pressure samples, @ eight different yaw conditions, six different frontal areas, ten samples/second, ten seconds/ configuration, @ fifteen simultaneous sampling locations
From the Cp formula, local flow velocity average mean @ the tailgate separation line was 127.59 ft/second
From the Cp formula, average mean base pressure was 26.936" Hg, 13.142-psi.
If Wolf Heinrich Hucho's neighborhood metric for a Cp = -0.20 'squareback' ( Ford Expedition ), then, the F-150's Cd 0.1825 indicates for a degree of pressure recovery, lacking in a generic squareback.
The Rivian R1, @ Cd 0.30, might illustrate pressure recovery due to a captured vortex over it's OEM bedcover, it's boat-tailed rear fenders, and full belly pan ( I've no details about any 'diffuser' ).
If CYBERTRUCK makes it to production next year, it will be interesting to see any actual test results. Theoretically, the Tesla will have the highest pressure recovery of any pickup ever offered. And would 'show', by default, with respect to highway range, on a pack size, frontal area, travel weight basis.
Owners, never interested in off-roading, could easily aero-mod CYBERTRUCK into the low Cd 0.20s. Lower with a trailer.