I run a 27-12 on my road bike with a 53-39 on the front, so the 25-11 seems to be close enough that the indexing is still ok. Unfortunately the new cassette has highlighted the 'well-loved' nature of my chain - it was all a bit clattery.Did you need to make any adjustments on your derailleur or are you running a 25-11..
Shucks. I don't think I'll be putting in that effort on every ride!..don't think I'll be challenging any of your runs....awsome power
Assuming my FTP is 95% of the 20 minute test power, that gives an FTP of about 294W. I've done previous 8 minute FTP tests on the rollers using a powertap wheel and TrainerRoad and this usually gives values around the 270W mark. My guess is that I was finding it more difficult to get to the higher powers on the rollers and spinning out a little. I've also realised that I've not calibrated the powertap in a while.
One thing I did notice was that the Kickr's calibration was WAY out when I first fired it up - literally in the kWs! I couldn't find a way in BKool to do the calibration, but TrainerRoad has a decent spindown recalibration. After doing that the numbers became a little more realistic.