Not sure any of us can answer that for you. Take a look back at your recent history of Ramps, and consider how you felt the following day. Typical plan progression adds a short and easy Endurance ride the day after a Ramp. If you have done something more in the past (or even with that default) how did it feel?
Like so much of this, it is highly individual. Some people respond well to an effort the day before, hence why Openers are a thing. For others, a hard effort just takes away from the pending work the following day. Think about any other instances where you may have had a short, but strenuous effort followed by something major the next day, and take your best guess.
As a passive viewer of Everesting, the approach seems to be start slower than you think you should and you will just slow down from there 
Kinda joking, but kinda not.
Even if you had a test at a more optimal time, I’d be cautious about taking the results for gospel without being very open to adjusting on the fly. Hard to know what you will really have in your hands on the day.
My point being that unless you think you are WAY off from your current FTP (consider the workouts in the prior couple of weeks and how those went), and you may be able to take a reasonable guess at your current state.