Having a “more accurate” ftp isn’t going to change the fact that you, like me, struggle with vo2max work.
Just keep it simple. Use the ramp test to set your training zones. When doing vo2max work, do what I do and just dial down the intensity.
Why is that ok? Because the first goal of vo2max work is to use enough power to force your body to demand a lot of oxygen (90+% of your max aerobic capacity).
Coach Chad’s notes say this as well, with different words:
Important: Try to settle on a demanding but repeatable power output such that you can finish as many intervals as possible. The goal is to accumulate a productive level of stress at a high level of intensity while avoiding the need to frequently quit intervals early.
Focus on repeatability before increasing power. For 3-min intervals at 120% ftp, during the workout you can dial intensity down to 95% or 90% or even 88%.
The first goal is repeatedly stressing your aerobic system, using just enough power above ftp to get your body to demand a lot of oxygen and force you to breath deeply to supply it. If you had a mask measuring oxygen consumption, your goal is to spend a lot of time above 90% max aerobic capacity. This really isn’t about HTFU and do the exact prescribed power (again, look at workout notes).
Sweet spot and threshold work are about muscular and strength endurance, where you really do want to use power and duration as the targets.
Hope that helps.