Maple syrup is 100% fermentable, and the vast majority of the maple flavors blow off. A technique I use is to add lower grade (B or C) maple syrup, which has more maple-ness, and add it at high krausen. The maple flavor remains tiny though, and tends to dry out the beer. Consider getting an organic maple extract and adding (careful not to over do it) to a sample, then upscaling the "dose" to the whole batch. That is the only way I have found to get the maple flavor I want.
It takes a couple of tries to find the flavor YOU are looking for.