This afternoon, I started trying to pull the remaining data from the last three of Titler's disks:
Pinball Fantasies, Disk 2 - Party Land / Speed Devils
Pinball Fantasies, Disk 3 - Billion Dollar Gameshow / Stones 'n' Bones
Ultima V - Boot / Play / Underground Disk
They are all non-DOS disks, and quite possibly the only way I'm going to recover the missing blocks is to copy them from another disk belonging to the same set.
With this in mind, I have this evening downloaded the most likely Pinball Fantasies and Ultima V disk images I could find using the links at HOL.