Belt Drive Design Problem

[yarden.saa]

Hi CD,
For the first time I am trying to design a drivetrain with belts. I would like to keep everything in the minimum size.
**I will attach a photo of the drivetrain I want to convet to belts.
We are using a direct drive with hex shaft. the problem is that Vex doesn't offer pulleys it the same diameter as the hex pulleys. adding a hex hub over the pulleys will make the thickness of the wheel+pulley+hexhub+bolts+nuts too thick. I looked at andymark solution in their AM14U, they made holes in their pulley so the hub will fit in the pulley. I am looking for a solution that will work with vex wheels because andymark pulleys doesn't have the versa key pattern. Andymark variety of pulleys and belts is pretty small so I can allow my self using it.