Well, since it’s now almost gone I’d better get to this follow-up.
The Imperial Porter ended up losing its crown. I couldn’t locate the WLP007 or any high gravity yeast in time for brew day (every homebrewer in the area was apparently making a kick-ass winter beer), so I had to go with a standard English Ale yeast (Munton’s) and work a 2 day starter to get enough cells to take on the porter. They petered out early, and the resulting ABV was only 6.1% which, while reasonable, left the beer extremely sticky sweet. It’s been conditioning well in the bottle and I’ve received no complaints, but this was not the beer I was targeting. Ah well. It’s tasty and drinkable, so I can’t be too upset.