Yes
http://bell-everman.com/products/lin...elt-linear-sbl

that is a link to the commercial version. belt stretch is limited to the amount of belt it takes to mesh with the bottom "rack" and go over the pinion so it should greatly improve a belt system. zero backlash apparently?

Kind of hoping someone else has done this system and can warn me of the pitfalls ... but if not.. ill do it and report back.