I have very little sympathy for those who build near a property line without surveying first. When I built a fence around my property, I bit the bullet and paid $600 to have my place surveyed. Every pin was where it was supposed to be, but my neighbor had hinted that he thought a previous owner had moved some of the pins, and I wasn't about to take a chance of him arguing with me in the future. I understand that neighborly peace can be a more important principle than the property line itself, so I'm not questioning your decision to let it slide, but I have also seen too many of these cases where a person's generosity with regard to property rights turned out to be his undoing. I hope that you don't become one of them.