Questions? Looking for parts? Parts for sale? or just for a chat,
The WD Motorcycle forum
Mine is closer to 155mm ctc Danny.
email (option): pes.sales@btconnect.com
I have a copy of a 1954 REME Technical Handbook for the M20 and it shows frame dimensions but not the position of the part you were asking for. I can email you a copy of the page if it helps in any other way.
email (option): orchard_c@sky.com