The fermentation curve has levelled out over the past 36 hours so I decided to add the first dose of finishing hops now rather than wait another 2 days as per recipe, which was adjusted (on batch) by reducing the primary fermentation step by 2 days and adding a 3 day cold-crash. The entire collection jar appears to be full of yeast now as opposed to just a quarter inch from just a few days ago, so I’m taking this as another sign that fermentation is done.
Over the past couple of days I’ve been thinking about how to get the most utilisation from my hops (and not have them sitting dormant in the jar) and in the end I decided to close the butterfly valve on all that dead yeast before slowly de-pressurising the Fermzilla and chucking the hops in via the top after giving them a cursory flush with 70/30. The idea here is that once the hops drop down they’ll sit on top of the closed valve instead of in the jar or on the dead yeast, which gives them longer exposure to the beer and minimises any biotransformation to whatever yeast is present above the valve. I can always give it a shake as well without disturbing the yeast in the collection jar, which will hopefully increase utilisation.