I bottled a Triple Chocolate Stout last December (2013), that I brewed sometime in November. I used Chocolate Malt, Hershey's Cocoa Powder, and Torani's Sugar Free Chocolate Syrup. I am sipping one right now.
My only suggestion would be, that in addition to your hops, keep in mind the cocoa adds a bit of bitterness too.
Tonight's sample was very tasty, chocolate up front along with very light smoke, adding coffee to the finish. I may do this beer again, but I might use only 1 cup of the Torani syrup. I am my own worst critic, and I believe the mouth feel is almost "thick". Not syrupy, but it may be the ale has more carbonation than I wanted, and it may be due to that. I usually prime to 2.0 or so volumes, and I wonder, even though there is no extra sugar, if the Torani syrup has something fermentable adding to the fizz.