IMO sometimes in life a compromise has to be made, we do not live in a perfect world no matter how hard we try. What if you install a tile with a slight bow of say 1/2ml which is well within in tolerance and the customer pulls it, what you gonna do then? Experience also tells me that some customers ( a small minority) will try and take advantage if they feel like they could get away with saving a few quid. So no, the customer is not always right....