Good news and confirmation !
The screws with thread size M18x1.5 are correct !
Screws with 40 mm thread length will do the job !
I’ve done two tests today.
One with a B1/B2 motor, one with an LTD Y1 motor.
Approx 15 to max 20 mm thread length is needed to “get in touch” with the crankshaft, when screw is turned into the rotor. To finally remove the rotor only very little additional length is needed.
Attached a picture of a puller screw with 50 mm thread length in the moment it has contact to the crankshaft.
Go ahead ordering the 40 mm long screws ;-)))