I have nothing on this front yet, maybe by year's end.
Right now am doing a 290w Zwift ftp for some workouts and a 295w for others in my "rotation". I'm floating between 158 lbs and 161 lbs.
I did the Rouvy Mt. Mitchell climb and strung together about 2:05 or so of 260w AP. That was very painful but "easy" in that it's almost like ERG mode since the climb is so steady and not a high gradient. So no real surges to steal your power production over that time.
I'm pretty sure right now I could do around 40min at 300w if I wanted to. But 40 isn't 60.