X2 Modifications

Has anyone done a 2 speed belt drive conversion on the X2 minimill? Tired of replacing stripped/shattered gears. Also looking at fitting a reversing switch, which wires are cut into? Am looking for the belt size and diameters of the pulleys used, searched Google, plenty of designs and details, but no pulley sizes. Can't work out how to get the speeds versus diameters, using the same size belt. Pulleys will be about 19 mm and 80 mm for low speed, looking to get around 1500 and 2800 RPM max, motor is variable speed. If someone could work this out for me, I would be really appreciative.:2tsup:

YES I FAILED MATHS at school :rolleyes:.

Thanks

Kryn