Advice on a Russian Imperial Stout and a first ever parti-gyle attempt.

Since the recipe that I have for a RIS is using the first running only I figured I would make the most of the mash, and try a parti-gyle for the first time. I listed below the grain bill for the RIS, and I am curious about your thoughts on the parti-gyle. What type of beer would this technically be if something other than a weak RIS, a dry stout? I figured that I would have fun with the parti-gyle small beer since it is basically free. I am planning using Cascade and Hallertauer hops with WLP 001. Would this be a horrible combination for a Stout? What about also adding 2 lbs of sugar to the batch at high fermentation just like a RIS? I'm open to any and all advice, thanks!

RIS Grain Bill

Estimated ABV 12.3%

13.50 lb Pale Malt
2.50 lb Munich Malt
2.00 lb Flaked Oats
0.75 lb Carafa II
0.75 lb Caramel/Crystal Malt 60L
0.75 lb Chocolate Malt
0.75 lb Smoked Malt
0.50 lb Roasted Barley
0.25 lb Black Barley
0.25 lb Honey Malt
22 lbs total

Parti-gyle

Estimated ABV 6.1% (An assumption of dividing the RIS ABV by 2)

Fly-sparge with 4.1 gallons, and boil down to 3 gallons.

0.50 oz Cascade at 90 min
0.50 oz Cascade at 45 min
0.50 oz Hallertauer at 10 min

You could call it a porter, I suppose. If there are still sugars left in the grain, and you have the time and capacity, may as well use them. I'd get an accurate preboil gravity before determining hop levels. Otherwise, I don't see any reason not to do this.

In order to get 12.3% from your first runnings, you're going to have to sparge. If you want to parti-gyle, your first runnings efficiency is going to be much lower, like maybe 50%. That's just an guess. I've never done anything like this before. Use your hydrometer to guide you.

Anyway, I think if you want a 12%er and a 6%er, you're gonna need more like 30# of grain.

Thanks guys. I will definitely be doing a bunch of firsts for these two batches. I didn't include that I would be doing a molasses and sugar addition to the RIS, so that is where the additional sugars come into play. However, I just got the word back from one of the guys who brewed this same recipe and he only got 9% for his final ABV, so good job spotting that. Maybe this will be a lot weaker than I thought, so I may end up with a smaller small batch just to a decent ABV out of it.
What specifically would make this a porter? I just tried a Porter hopped to the levels of an IPA, and it was outstanding.