I will agree with you that the bass has a longer growing season so typically speaking bass will be bigger in the south. That is largemouth and smallmouth bass. Here we have a lot of sportsmen fishing with guides for our smallmouth fishing. As well as the fact for a bass over 5lbs. would have to live for a longer time to reach that wieght. We still do have some that will exceed this but they are not as common.
Now fishing them with a flyrod two of my favorites are the poppers which when brought in can look like a minnow. Then the hair made mouse which looks like a mouse that you can skip along the lilly pads and the like to draw a large bass out. It is hard to beat catching anything on a flyrod..