My best 20 minutes in the last couple months was 320 W according to Strava (powertap hub power meter). Injuries (and tumors) and life changes have gotten in the way in the 6-7 years since I was last at peak weight and I'm now up to ~107 kg, so 320 was only ~3 W/kg. My 95% average of my best 3 is more like 305. Those are from ~30 minute races, no way I could hold that for an hour.
I get tired of the folks saying that flat races on Zwift are all about pure Watts so that I have an unfair advantage in Cs. On a flat TTT where we have it set so that the puller is going at constant speed instead of constant W or W/kg, I put out 50 or more W than the little guys to maintain the same speed when pulling because of my much bigger cDa/friction/whatever.