i have had to hire a surveyor 3 times in the last 6 years to define property lines. the first time, the neighbor had 5 1/2 acres of mine. the previous owner didnt know. but a half mile long boundry, where you are losing a slice that is around 100 feet at the widest to around 20 feet at the narrowest adds up. get it legal. a surveyor is a good start.