Need advice - imperial stout - yeast

[JaymzMF]

Need some advise. I’m brewing a 10-11% ris this weekend. Wanted to try out the darkness yeast from imperial yeast. That was always the plan. But... I have a 6% APA in my fermenter now which used white labs wlp001. Hasn’t been dry hopped yet.
I’ve heard of people pouring new wort right onto yeast cake. Is this something I should consider? Or build my darkness starter as planned? Pros and cons of either one?
Also if I did use existing yeast cake, I can’t clean the fermenter. Just reuse and not worry about cleaning?
Would really love to get your feedback on this. Not sure what to do. Thank you!

 

[CascadesBrewer]

Some people pour into the yeast cake without cleaning their fermenter. If it was me, I would transfer off 16 oz (maybe 32 oz) or so of the yeast slurry and pitch that into the next batch. If you decide to pitch directly onto the cake, I would just make sure to limit the time your fermenter is sitting around empty.

I have not used Darkness (similar to 1084?) before and have never used a Chico yeast in a big stout, but both seem like good yeasts for the job.

Good luck!