How much flaked rye?

I'm brewing a dry stout tonight, and my lhbs didn't have any flaked barley, so I decided to go with rye instead. My grain bill thus far:

8 lbs pale malt
10 oz chocolate malt
9 oz debittered black malt (yes, I know these last two are weird amounts, but I'm also kind of using up stuff I have on hand)

To this I was going to add 1 lb flaked barley, now thinking I should go with about 1/2 lb of the flaked rye. Any input?

 

Question: why are you adding it? Head retention? (Rye won't do as well; flaked wheat would probably be a better substitute.) Flavor? (You might want to add more like 1.5 to 2 pounds.)

 

thanks for the reply, but I read it too late.. I'm already mashed in.

The flaked barley was supposed to be for head retention. When I was denied that, I went with rye because I've never used it and I've been wanting to. I went with flaked because I crush my grains the night before, so I wanted to stick with something I didn't have to crush today. I guess I'm using it more for flavor, and I figured it would go well with a dry stout. So I only used a half pound, not sure how strong the flavor. But no worries, I reckon the worst it can do is have no discernable effect.

 

Flaked oats (quick oatmeal) would probably be better for head retention but it might leave the beer hazy. It might be hard to tell with a stout.