Conversion of Partial Mash to Extract Recipe?

Can some one help me out? I don't have an all grain setup. I have been brewing extract for a few years now. Can I just hold the temp and put the grains in a bag and steep for 90 minutes?

Smoked Chili IPA
(5 gallons, partial mash)

For the beer drinker who has tried everything before, just to prove that he or she hasn't. This beer is malty and fairly big underneath and hoppy in the middle, with a waft of beechwood smoke near the end. And, of course, you get dragon's breath for hours after!
Ingredients:

* 3 lbs. pale malt
* 1 lb. toasted pale malt (toast in oven for 30 minutes at 350°F)
* 1 lb. beechwood smoked rauchmalt
* 1 lb. medium crystal malt (50° to 60° Lovibond)
* 4 lbs. unhopped light dry malt extract (DME)
* 2/3 oz. of 12% alpha-acid Chinook hops (8 AAUs)
* 3/4 oz. of 8% alpha-acid Perle hops (6 AAUs)
* 1 oz. of 4% alpha-acid Kent Goldings hops (4 AAUs)
* 1 oz. of 4% alpha-acid Fuggles hops (4 AAUs)
* 1 large dried Anaheim chili o English ale yeast slurry (Wyeast 1098 or equivalent)
* 1 lb. oak chips (optional)
* 1 cup light DME for priming
* 25 medium dried Anaheim chilis, cut in half

Step by Step

Heat 10 quarts water to 164°F. Crush grains, mix into liquor and hold at 152°F for 90 minutes. Runoff and sparge with 15 quarts water at 169°F. Add DME to kettle, bring to a boil.

Total boil is 90 minutes. Add Chinook hops, boil 30 minutes. Add Perle hops, boil 30 minutes. Add Kent Goldings hops, boil 30 minutes. Turn off heat, add Fuggles hops and 1 dried Anaheim, chopped into small pieces.

Steep 30 minutes. Remove hops and pepper, chill wort. Steam (15 minutes) and toast (350°F, 30 minutes) oak chips, if desired, and place in fermenter. Add wort to fermenter along with enough preboiled and chilled water to make up 5.25 gallons. At 65° to 68°F, pitch yeast.

Ferment relatively warm (68-70°F) for two weeks. Rack to secondary and condition cool (55-60°F) for three to four weeks. Prime with DME, add half an Anaheim pepper to each bottle. Seal and condition for six weeks.

OG = 1.070 (17.5° Plato)
FG = 1.020 (5° Plato)
Bitterness = 55 IBUs

A 90 minute mash is pretty long- it might be hard to hold a steady temperature that long. You only have to do it long enough to get conversion- in my mind, 60 minutes would be more than long enough.

You can get a big grain bag (or two, if you can't find one very large one) and put the grains in the bag loosely and steep as described. Use 1.5 quarts of water per pound of grain, and keep at 152 for an hour. Make sure to stir well, thoroughly wetting all of the grain. Make sure the grain is loose in the grain bags, not packed, so you can stir it even while it's in the bags.

I don't think 1 lb of rauchmalt is enough for the flavor to come through.

I just made a Kaizerdom Rauchbier (Clone Brews) with 1 lb and it's barely perceptable. I'm going to make another batch (smaller) and use 3 lbs then blend them. It should have enough rauch flavor then without it tasting like a Schlenkerla Rauchbier.