It works well with the chain. The pulley openscad file had to be changed a bit to make it remove less of the sphere so it held the chain better but other than that it seems fine.

For the first couple of hours running I had to keep adjusting the tension but after that it has stayed tight. I left it running like the video overnight with no problems or slipping.

http://homepage.ntlworld.com/dknpower/chain.mp4