When I worked through the cost of r&p some time ago the cost was comparable or even a bit more than ballscrews from china. I didn't shop around too much but I still know which way I'd go! Again jazz is right cost saving on angle and v bearing compared to Chinese supported rail does not make it worth doing.

I too was planning on mdf base as I haven't done much metalwork - I have decided to learn though! It takes a lot of effort to build one of these things and you might as well do it right?!