In the end, I've decided to go through my journal, and fix everything (which is taking a while). The main auto migration that is actually causing me a headache is the racial hit dice. I've got plenty of creatures and characters that have suddenly doubled in hit dice. All my creatures have been created with racial hit dice added as class levels. So a Roc is created as a 16th level Animal. After migration, it is listed as a 32 HD creature - Animal 16, plus something unspecified 16. A Troll Witch (Giant 6, Witch 10) is now listed as level 22. I'm removing the new racial hit dice for now, because there's not a clean way of removing class levels for characters with multiple classes. Which brings me onto a related point - the racial hit dice are coming from the 'Race' field, but shouldn't it be coming from 'Type'? The only creatures I've given a race to (and this may be just me, but it seemed the sensible way of doing it) were humanoids, e.g. Human/Varisian, or Human/Shoanti. Their type was set to "Humanoid (Human)". Animals have a type of "Animal", but no race. The racial hit dice should be Animal, Outsider, Monstrous Humanoid etc, which is defined in the Type field, since it's the type that defines BAB, Hit Die, Skills and Saves. Defaulting hit points to be auto generated also causes problems, because some NPCs who I had actually rolled hit points for have been forced back to having average hitpoints. I'll need to go back to my backup to find original values. However, one up side is that the Hit Die field is quite useful, and it's allowed me to write a simple script that randomly rolls hitpoints for individual mook tokens (so, a band of goblins can all have different hitpoints). So thanks for that.