My second beer was a brown ale with 64oz of maple syrup added. Holy crap, it was not what I expected. The OG was 1.078, with a FG of 1.011. The maple was so strong that it had this slightly gaggy roundness to it, kinda like eating too much melon at one sitting. However, after a year of aging, the weirdness of it has dropped out to make an interesting stout-like brown ale. Certainly deserves the title of "Imperial."
If you haven't made this already, I'd recommend 16oz as a starting point. OR, you may just have to do some serious aging.
Lemme guess, you read (like I did) in Papazian's book how he recommends at least a gallon but oh how that hurt$? I remember being a new brewer and thinking, "Holy crap, I can ferment ANYTHING!!!!! Let's put everything in beer!!!!!"