Stoker seat post diameter on Burley Tamborello?

[mystrwizard]

I am thinking about buying a used Tamborello and dont have access to one but would need to attach a child stoker kit to it. I machine myself so am going to make the bracket that attaches to the stoker seat tube on the bike but was wondering if someone could give me the OD diameter of that tube?

Thanks!

[ElRey]

ask Burley