FNW - you would have to have some definition of what useful payload is - MAUM minus ZFW or MAUM minus Basic Wt or some other figure to apply that 40% - it sounds like a typical manufacturer's fudge. Is there an increase of 40% over the mass for OGE hover OEI using 2 min power?
As for MFTS - which continues to be so bad the students have released a 'music' video about it which is doing the rounds on Whatsapp - I don't know if they have that engine mod or not, just that the 145 is a retrograde step from the 412 for winch training.
Sas - apparently the Whirlwind used to winch itself down to the casualty! You do know the RAF stopped using those many, many years ago???