Rolf
I am aware that more mast rake lenghtens the distance and more spi-pole height shortens the distance and that usually there is not a 90deg angle between spi-pole and mast (in the REAL world my guess the angle is less than 90deg).
My indication was aimed only to enter in the ball-park.
On a different note I appreciated very much yr info about the "correct" width of the radial panels.
This is the kind of info that we should share on this Forum.
I agree in full with you:
it's VERY surprising that so few participate and show interest when these kind of discussions pop up from time to time.
Only these discussions can make us better catsailors!