I'll be there Davey, just not riding, saving myself and the pocket for my skiing holiday the week after.
I gave the thickness some thought, there's still plenty of strength in the lever, the steel they use in those levers is also high tensile, I went about 2.5mm wall thickness of the sleeve which still left on average about minimum 4mm of wall thickness on the lever.
It was a little delicate with the lever flying around, that was the only problem, I was restricted to about 250rpm. I could have spent more time and added a counter-weight, if I were to do more I might go there.