Vyse change with weight?
This might be difficult to explain using text ... but ...
I've always assumed that, to a first approximation, Vyse will vary with weight (and therefore Lift); so Vyse at Weight W1 can be estimated by modifying the Vyse at MAUW by the ratio of the SQRTs of W1 and MAUW. Obviously there will be a small form drag element that's not lift-related, but what else is significant?
If it were only weight related, a Vyse of 90 at 4200 becomes a Vyse of 78 at 3200 - and I don't believe that!
HFD