Thanks, @HLaB intervals.icu looks great. I am just not sure I want to sign up to yet another platform (even if it is free). On FFT, there only seems to be a calculator sheet based on best 20’ power.
I think this is it but my internet is playing up with it:
FFT Magic Power-Duration Curve (FTP) Predictor [Link: fft.tips/curve] - Google Sheets
This is it Thank you, @HLaB
Based on the Alpe effort the FTP60 prediction is 348W - which sounds about right.