I reckon your FTP is about 310 (but now rising)
Zwift had me pegged at 326 last summer, but it’s set at 316 at the moment.
Wednesday I had the turbo set at 320 and managed 15min at that with a view to finishing the whole ride, 20 wouldn’t have been nice but it would have been doable if that was it, not sure I’d have managed 20min at much above that though, so somewhere about 305 at a guess.
Last night was supposed to be 1.5min on 5off 2/5/2.5/5off & 3on at 125% & 90% respectively so effectively 24min at about 103% ftp avg. (so a little below 20min best for 24 minutes) It is do-able if unpleasant assuming the numbers are right.
If my guess work is right on 305ish it works out at 130/95 ish and about 108% (a bit above 20min best for 20% longer) which might not sound much…
I’m torn about doing a “proper” test or just slapping a 1hr block in at 305 and trying for the end of it.