I have dug out my very old seitz kit and measured everything. The 2 sleeves, one for the reamers and one for the pushers are 8mm diameter. The stumps have a 3mm fitting. The pushers a 4mm fitting and the reamers have a taper fit which is 2.5mm at its widest. Hope thats a help!?
Welcome aboard Legarm.
This is a great forum to be part of and there is a huge knowledge base amongst the members that can be tapped when required. Well done for what you have achieved given the time and circumstances. I'm sure it won't be long until you delve into chronographs, which are a passion of mine. :-)