Oh, and I guess I should add that in my dub collection, most were synced to or derived from NTSC video, so trimming video would actually improve their sync too.

The only ones in my dub collection based on either PAL or some unknown frame reference are: Czech, Hungarian, German, Italian, and Russian non-voiceover. Pretty manageable if we want to check/fix them, but I honestly don't think a fix is needed. And we'd have to go back to original sources because all I have is lossy versions, and we'd lose more quality from lossy recompression than we'd be gaining in sync.