Thanks for clarifying the batch volume. What you currently have might be fine for a RIS, but if you're trying to emphasize the "chocolate" in chocolate stout, I stand by my advice: I'd dial the roast grains down to around 1 lb (or less) total per 5 gallons or cold-steep the amount you are using.
I recently did a 10 gallon batch version of JZ's Black Forest Stout (Brewing Classic Styles, pg 282-283).
JZ's 5 gallon batch version called for 0.75 lbs Black Roasted Barley (500 L), 10 oz. Crystal 40, 10 oz Crystal 80, and 0.5 lb Chocolate Malt (420 L) for the darker grains. British Pale malt completes the grain bill.
My adaptation used 0.67 lbs each of Crystal 40, 60, and 80; and 0.5 lbs each of Chocolate Malt (350 L), dehusked Carafa I (337 L), II (412 L), and III (525 L). I was hoping to reduce some of the bitterness/astringency associated with the use of Black Patent malt usage. Pale malt completed the grain bill (along with 1 lb of melanoiden malt). I mashed all the grains together at 158 F x 45min. 1 lb total of cocoa powder and 4 oz. cocoa nibs were added in secondary and left for 4 wks/2wks respectively. Black Cherry Juice (RW Knudsen, Just Black Cherry) was added at bottling [64 oz/10 gallons].
There is no mistaking the roast character of the stout when I (or others) judge it. Is the astringency less than it would be with the use of Black Patent malt? Maybe. I still think it would be "smoother tasting" if the dark grains had been cold-steeped. The roast still nearly overpowers the cocoa flavor and aroma. The cocoa nibs likely add bitterness of their own (taste one yourself). The feedback I get tells me the stout base was fine, the chocolate flavor was OK, but the bitterness/astringency and the cocoa aroma was too high, and the body was too thin (probably due to dilution by the cherry juice--I did not have access to good cherry puree). That tells me to cut back on my dark grains significantly if I am going to use the cocoa nibs again. The temp has to be above 50 F to even pick up the cocoa or cherry flavors. The roast predominates otherwise.
Just my 2 cents. Good luck with your recipe.