I’m in the same boat as you. I don’t think very many people are banging out 5x5’s at 120%FTP (i.e. you’re totally normal in this regard). I’ve been on a VO2 Max kick lately too (reading up on it). Most of the consistent advice I’ve seen is about getting that HR up above 90% HR Max and the power isn’t as important. People doing 5x5 might start the first interval at 120% FTP, but from what I’ve seen in this forum, the actual power in subsequent intervals drifts downards, and that’s okay becuase the goal of VO2 workout is about getting you in that ‘breathe like a fish out of water’ physiological state.
That being said, I get into that state doing 5x3.5-4 minutes at 110% FTP target. And it’s been great for my FTP this base season. Good luck!
This was a good thread for me. it’s quite long tho.