Andy, sounds like the trowlers may have 'cheated' a little too much (*dirty little secret* - we all trowel the bottoms a little lower than the specs call for to insure that there are no wrinkles in the liner, the liner can handle the ~ 1/8 - 1/4" stretch, however if you overdo it, the liner can't stretch into the corners). Another possibility is that the liner wasn't cut correctly at the factory. I'm not trying to say that you've gotten a 'bad' job done on your pool, it will probably never become an issue for you, but I would point it out to the installer, the liner is more vulnerable to tears when it is not backed up by something solid. Having done that, I'd just enjoy the pool - Ted