SU piston stop cushion

[40GT]

Anyone know the tolerance for the nylon stopper insert on the piston underside, ( damper cushion for piston drop to throat bridge ) , the SU part number for the smaller carbs is AUD 2435 and the air gap is 8 - 12 thou, but I think this is only for HD4/6 carbs, the HD8 having a separate air bypass which avoids the possible piston drop engine stall effect.
I will call SU tomorrow, but just thought if someone here has already been here.