Hello!

From where do you have these values for nozzle flexibility? I think this flexibility depend on the pump dimensions. I usual make the stress analyze with pump nozzle modeled as anchor, or imposed displacement node (if I have data for it). I model the pump nozzle as flexible anchor only when I have data for it from the pump provider.
In the most cases the stress analyze with the pump nozzle modeled as an anchor is conservative.

Best regards,
Dragos