OK in 1955 M20 had a one inch monobloc fitted and it had a 240 main jet, 30 pilot jet and 106 needle jet and a number 5 slide. This is from Amals book. Regards John

don't know if this helps but on my M21 I have a 1 1/16 " Monobloc with:

Mainjet 250 (270 without filter)
Pilot jet 30
Slide #5

seems to work OK

The M21 settings as you have stated are correct for the 1957 to 1961 M21 as per Amals book so will be fine for any M21.