Followup question: with an FG of 1.029 is this going to be like syrup? The biggest problem I have with imperial stouts I've tried is they are too sweet for my taste. Should I use a more attenuative yeast like WLP007 (Dry English Ale)?
I think 1.029 will taste sweet, but maybe not like syrup.
I have a quad fermenting right now with a similar OG to your recipe that stalled at about 1.025 and it was very sweet. Too sweet, for me. But I like my beers strong and dry.
My old ale also starts around the same OG and tends to finish around 1.015. Definitely not overly sweet at that FG.
The alcohol should offset some of the sweetness, but I'd go for something a bit more attenuative.