First attempt to doctor up an extract kit.

WLP 007 MUST have a starter. I wouldn't trust 2 vials to do the job. If you underpitch you'll end up with a FG that's too high and you'll end up with a fusel alcohol bomb. Mrmalty.com will help with this.

Ferment in the low low low 60s and feel free to bring it up to room temp a few days after high krausen.

 

I am confused by the addition of Maltodextrin & pure sugar. They seem to be conflicting in their purposes. Generally maltodextrin is used to add body to beer as it is unfermentable, while sugar is used to dry out a beer...

 

I wouldn't trust 3 vials.

If you're shooting for a 5 gallon batch you are talking about 300+ billion yeast cells. This will call for a stepped starter. The yeast calc on brewersfriend is actually a little nicer than mrmalty for this purpose. And if you don't have a method to add oxygen (not air) expect some major under-attenuation. May as well learn about this now.

 

Batch size? At 5 gallons, this is a monster of an imperial stout. Beers this big are not my style, so the following advice is based more on what I've learned through reading than through brewing: there is so much fermentable in there that you really will need to pay attention to pitch size and health (multiple yeast vials, starters, oxygenation, temperature control). My closest experience to a beer this big was a mead, and it was a fusel bomb that ultimate went down the drain. Ingredient cost was >100 bucks, so this was not an easy pill to swallow, but it was easier to swallow the cost than to swallow the mead.

As for ingredient choices, if you know you like that blend of roasted and crystal malts, then fine. In newbie recipes for stouts, it is very common to see black malt, roasted barley, and chocolate malt, simply because those are the 3 main types of roasted malts and the newbies think they are "layering" flavor. If you are just guessing at the combination of grains, I would dial it back to one or two types. That way you have a better chance of identifying whether there is something specific that you like or don't like. Bear in mind that maltsters can vary a lot in the degree of roastiness of any particular malt.

And now to the matter of crystal malt. For a beer this big, maybe 1.5 lbs of crystal is OK. Usually I keep it at 1 or less. But that's a highly personal preference. You will learn what is best for you and make your beers accordingly.

 

Huge amount of fermentables. You need multiple vials and a starter and you need to baby that fermentation or you could end with something that is underattenuated or a fusel bomb, or maybe even both. Read up on starters at Mr Malty and I strongly recommend learning more about controlling fermentation (e.g., yeast, by White and Zainasheff).

I assume you are using three roasted grains because there are three main types. Sometimes more is not better. You will need to learn for yourself because this is a matter that will vary from palate to palate. A lot of folks bash black malt for being ashy. Some bash chocolate malt for bringing too much coffee-like acidity. Of course, details will vary by maltster and ultimately you need to decide what you like. I think it is harder to do that when you start out with the kitchen sink.

For a big roasty beer, 1.5 lbs of crystal malt may be appropriate. This is also a matter of personal taste that you'll need to figure out. You'll get about 60 bus of hops in this, which might be right for a beer this big. You'll have to decide for yourself, but I think it is a reasonable place to start.

 

I would recommend you use one of the yeast calculators. Arbitrarily deciding to make a starter (how large?) with two vials and pitching one vial direct is just shooting in the dark.

 

You are taking a high gravity kit and increasing the gravity by 25% or so.
The added DME concerns me, but you clearly want a huge beer. Since I don't make big beers I won't give you advice, but there have been some articles in BYO on high gravity brewing that you can find on line.

 

I like the use of all 3 roasted malts, but black patent definitely has some ash notes to it. This beer will likely need a lot of aging and the ashtray will fade/blend over time.

I'm more nervous about your fermentation temps. You say a room in mid-60s, given the size of this beer your fermentation temps could easily hit 75 if the ambient temp is 65. If you really want to brew this, you need a way to make sure your actual fermentation temp doesn't rise much past 65 or you will have a drain pour. Look into getting a large cooler, you can add frozen water bottles to control the temp.

I would consider a dry yeast, much cheaper to get the amount of yeast you will need.

 

Not to go off on a tangent, but why did you choose to doctor a kit when you could have bought the ingredients individually, probably fresher, and for less money? You're basically doing your own recipe anyway. It reminds me of a relative of mine who, years ago, was so proud of her home-made red sauce. I'll admit, it was tasty, but there was something 'store-bought' in the flavor. I once watched her 'make' it. It was a jar of Ragu which she doctored by adding various spices. When I asked her why she didn't just buy tomato puree and make real home-made sauce, using the same spices, she really didn't have an answer. Her red sauce improved dramatically after that conversation.

 

I'd offer up the suggestion to use some dry yeast. US04 would be your best bet, to make sure you pitch enough cells.

Also, I'd suggest splitting it in two carboys and for the love of everything, you will need to keep it cool. Low side of the suggested fermentation temp. 65 ambient isn't gonna cut it, IMO.

 

If the weather forecast calls for under 70-ish for the next few days, you could safely ferment in the garage. Nightime temps should keep it cool enough to survive daytime spikes into the low 70s.