Hi guys!
Thanks to all for your help! It was quite a challenge but in the end I got values that work:
M92 X87.9328 Y87.9328 Z3980.
This will bring the extruder to exactly Y=140 and Z=10 (the biggest I could measure precisely).
So I'm happy again! Now, I will try to implement mesh bed measurement!
Again, accept my deepest thanks to you all and to this great community!
Ciao,
Bob