Are there any advantages to using metal post spikes set in concrete when building a privacy fence?
The main con is that since its designed to be driven down, the tapered tip will offer less torque, even set in concrete, than a post set to a similar depth.
Another consideration is frost heaving.  The bare adapter should not heave, but the combined concrete/adapter might, unless the pour goes below the frost line.  This can be mitigated with SONOtubes use.
I wonder if using 2 ez-mender, set in concrete, might not give a more stable base.

(from the website: &quot;Post bases do not provide adequate resistance to prevent rotation about the base and therefore are not recommended for non-top-supported installations such as fences or unbraced carports&quot;)