Hello Howard,
in my actual Excel sheet I did the calculations in the analytical way. I will switch it to numerical, so I can include corrections for the Aspect Ratio, as proposed in Schrenk. Thanks for the link!
Regarding the variable pitch control, I use my own timer to keep the rpm constant (Controline mode CC Phoenix edge lite 50 A), and to adjust the pitch so that the line tension stays constant overhead and level. Flights are planned for the coming weekend.
Best regards,
Wolfgang