@Tenacious
I had the same problem with the last release of pfs3 about 5 times on my A4000T and that's using a 2 types of scsi drives and even an ide drive, after speaking to the developers when OS3.9 came out, they advised me to accept the defaults settings using HDToolBox when setting up the drives.. i questioned the settings but they explained how hdtoolbox looks at the drive using it's own calculations.. which are correct even though some people think they are not.
Also PFS3 doctor i found makes things worse..