I developed this recipe for a 6 gallon batch knowing that 1/2 a gallon will be left in the pot to avoid as much trub as possible. That said you will be fermenting 5.5 gallons.
All rest temperatures are in the tun, not strike water. You will need to calculate your strike water based on your grain temperature and type of mash tun you are using.
I use yeast starters in all of my recipes with what I think are excellent results. For my starters I compose the starter wort to closely approximate the sugar profile of the target batch. This helps the yeast develop the best cell membranes to ferment the final wort with little to no adjustment. I typically use a 1 quart starter for gravities 60 and above, and half quart for gravities below 60. I allow the starter to ferment a full 3 days to allow glycogen reserve buildup and settling. Then I pour out the first little bit of starter, pour the middle bit into a glass, then pour out the rest leaving mostly only the yeast cake. Then I smell and taste the bit in the glass to ensure there are no infections lurking. Sanitation is paramount.
I've brewed this batch a number of times. It is not at the high end of the Imperial/Double IPA spectrum, but it gives the drinker all the in-your-face hop aroma and flavor one could want, backed by balanced malt flavor and body. The Warrior hops are the cleanest high alpha hops I've found. Using them in the FWH and the boil set the foundation of the hop character of this beer. And while the remaining additions are all Centennial hop additions, because of the times and the fact that Centennial is already a complex hop, you get all the complexity you need. If you want to swap out for the other American "C's" (Citra, Crystal, Cascade, etc...) all of them will work well, but give this a go first.
Give this bad boy 10 days in the primary at 64-65 degrees, then rack to a secondary. Let the beer condition for 2 more weeks in the secondary, then add 1 oz. each of Centennial & Willamette whole hops for 1 additional week of conditioning with dry hops. As an alternative to 2 ounces of whole hops in the secondary, you can leach/rinse the Willamette hops with a small amount of boiled water or even better a boiled bottle or 2 of beer. I use this approach to add 1/4 ounce of Polyclar 10 with the boiled beer.