As far north as maine is and you stating they are new to the area I think you are probably being fed some fibbers... that and the fact maine's state record is 11lbs caught in 1968!
This part of Maine they are quite new as they were introduced illegally into some of our trout and perch waters. When I say quite new I am talking within the last 10 years. Though the biggest one out of Pocomoonshine Lake has been 10 pounds so far most are only 6 pounds and under. Boyden Lake during ice fishing season a couple 8 pounders have been caught. That is it for as far as largemouths in this area is concerned..