This Sweet Spot progression is working wonders!
Did a 60 minute interval @ 92% today. Challenging, but by no means my max for TTE.
Power PR on everything from 22 to 60 minutes 
Not sure why, but my cadence naturally drops during these kind of intervals. Somehow it feels easier going at low 80s or high 70s for RPM outside. Legs do feel a bit fatigued afterwards, but nothing crazy.