Maple Syrup Question

I just attended a beer tasting in Chicago where I tried a lot of great beer, but I have been dreaming of this brew I had from Hamburger Mary's. It was a Rye Pale ale brewed with maple syrup. I decided I wanted to brew something similar. I have never brewed with maple syrup. I am planning on adding the syrup to the secondary, I was wondering about how much to add to get a subtle maple flavor. I have heard that the darker the syrup the more flavor will be imparted in the beer. I know that most of the syrup will ferment out and won't add much flavor, but I am not a fan of using extracts for flavor. Does any one have any advice on how much maple syrup for a 5 gallon batch?

I would suggest searching for maple here in the forums. You will get a healthy ammt. of results with many opinions. Mine is grade b in secondary or priming.