i don't really know, but i can't imagine pulling the seal via the rubber, bec i'd imagine the rubber just ripping out. and when i did it with an angled screw driver and hammer, it popped right out. no damage
i'm only guessing on them being 'drain' holes, and i haven't found an explanation otherwise. and i haven't found any mention as to discarding the locking plate, bec it'd be useless after the conversion ?
