First stout. please critique (BIAB)

I'm hoping to get a chocolate milk mouth feel and taste. I've never used any of these ingredients, so I would like some advice. How far off am I?

Title: Temporal Fracture Chocolate Milk Stout

Brew Method: BIAB
Style Name: Sweet Stout
Boil Time: 60 min
Batch Size: 5.5 gallons
Boil Size: 7 gallons
Efficiency: 65%

STATS:
Original Gravity: 1.056
Final Gravity: 1.014
ABV: 5.5%
IBU: 38.61
SRM: 39.67

FERMENTABLES:
10 lb - Maris Otter Pale (76.9%)
1.25 lb - Chocolate (9.6%)
0.75 lb - Flaked Oats (5.8%)
0.5 lb - Caramel / Crystal 60L (3.8%)
0.5 lb - Roasted Barley (3.8%)

HOPS:
0.5 oz - Millenium (AA 17.5) for 60 min
0.5 oz - Mount Hood (AA 4.8) for 30 min

MASH STEPS:
1) Infusion, Temp: 153 F, Time: 60 min

OTHER INGREDIENTS:
1 lb - lactose , Time: 10 min
*taste at bottling, not "chocolately" enough, add chocolate extract. (How much?)

YEAST:
Wyeast - London Ale 1028

Bottle Conditioned, 4.5oz priming sugar.

Generated by Brewer's Friend - http://www.brewersfriend.com/

I've made a stout with a very similar recipe, only differences in the grain bill were 1 lb of chocolate instead of 1.25 and 1 lb of oats instead of 0.75. I really enjoyed it, and I really think a lb of lactose would have only made it better. I'd honestly skip any hop additions past 60 min, you really won't be trying to draw anything from the hops, so just maximize your IBUs with a single bittering addition.

I agree with phenry, for a sweet stout, especially if you add chocolate, hit your target IBUs only with a 60 minute addition.

As far as the chocolate, if you want a chocolate taste, there are probably better ways to go than extract. I've had success aging beer on cacao nibs, others use cocoa powder either at the end of the boil or at bottling. How much to use would all depend on how much of a chocolate taste you want. 2-4oz seems to be pretty subtle, 4-8oz is a common amount for a noticeable amount, and 8oz+ gets a lot of chocolate flavor. If you do a search for cacao nibs or cocoa powder, you should be able to find a lot more in depth detail.

I'll edit to only include a single stage of bittering hops when I brew. Thanks! I've actually looked into cocoa powder, Baker's chocolate, and cocoa nibs but I've heard they can impart a strong bitterness. Any truth to that? How much chocolate flavor can I expect for it being ~10% of my grist? I've only brewed lighter beers to this point and use 80/20 RO to tap water. My tap water is rather hard but I think I've read that's better for a stout? Should I do a 50/50 RO to tap? I can post my water profile if that helps.

Well, chocolate is bitter, the darker, the more bitter. But that's not bad, it goes well with beer. The few times I've used nibs, I haven't noticed any unpleasant bitterness. And having 1.25 lbs of chocolate and .5 lbs of roasted barley will give it a nice roasted character, similar to the roasted, burnt flavor of cacao nibs, and it can taste kind of chocolate-y, but if you want a distinctive chocolate flavor, you'll need to add cacao or cocoa.

I don't really know much about water profiles, but you probably will need to post it to get good advice.

With that much roasted grains you'll probably be fine no matter how hard your water is, but feel free to post up your profile anyways. I'm definitely no expert on water chemistry, but I can probably do enough so as to point you in the right direction.

Ca+2: 35ppm
Mg+2: 17
SO4-2: 9
Na+: 2
Cl-: 4
HCO3-: 225

Yeah that's definitely not too hard for what you're doing with this recipe. But wow, does your water have a ton of iron or potassium in it or something? That's a really high anion concentration for not many cations... If you do feel like messing around with water chemistry, try maybe adding some calcium chloride? Chloride is supposed to accentuate fullness and sweetness, so maybe something like 0.2-0.3 g/gal of liquor? I'm usually pretty conservative with my additions, so that may not be enough to really make a noticeable difference.