Again, thankyou for the detailed reply irving.

Your point about the stability being better with the bearing "upside-down" is pleasing to hear. This was how I was thinking of doing it. The rails on the base and the bearings on the moving bed. I'd assumed it would be better so as not to get any twist or bow in the bed. I also thought that by doing this, the bearings would be protected from dust as best as possible.

I think I need to stop thinking so much and start cutting some wood. lol I get to the point where I am happy with a design idea in my head, but then I try and over-complicate things and it changes again. I have the remaining wood I need now to finish my benches in my workshop (garage) so if I can get them all finished over the weekend I'll be all set up and ready for some parts with this months pay :)

I'll be going with green MDF and some aluminium angle as my main construction materials. I'll start a blog as soon as I cut something. Nothing spectacular like some I've seen on here but for a first build for me personally it'll be good fun! ;)

Thanks again
Paul