To my knowledge flaked is raw. The raw grain is pressed to allow the enzymes from the pale malt entrance to the starchy goodness locked inside.
Some where a while back I had read that the Guinness brewery used to use flaked barely so to me this isn't that big of an issue. The article went on to say that presently the brewery buys all of its grain and then separates some raw and then malts and roasts the other. So the amount that the brewery roasts the grain is now a factor also. The raw is milled with the rest of the grain in new state of the art mills with extremely hard mill heads. Since my mill is well.... it's not state of the art, the flaked is the only way to go. I also used Wyeast's Irish Ale.
The method of using the malt vinegar has gone well so far. I have yet to do a side by side taste test with Guinness, but it tastes quite good. I haven't approached the sourness level of Guinness because I'm looking for other off flavors when I do this. I'm convinced that the chocloate flavor will mask any off flavors when aged in large quantities. Right now I just pour enough malt vinegar to cover the bottom of my pub style thick pint glass. I then dispense the beer on top, this gets the vinegar mixed into the beer. It also gets any off the sides of the glass, which eleminates any vinegar smell.
Currently I'm mixing an extremely watered down lawnmower beer with the stout. About 10% of this is added at the top of the glass. I then call the mixture EMF Guinness. If this beer is tried without the lawn mower beer and any sour the brew seems a bit roasty, but with the sour, and nitro its great!
I know that mixing beers may be a cheat. But it gets the flavor where it needs to be. I'm going to change things around a bit, but in the end mixing at the tap may be the only way to get as close as this mixture tastes IMO.
After brewing that other brew Let me know of your impressions and any adjustments. Thanks