wow, thanks for that irving. I think I understand the equations.

Do those 2 system numbers give everything that will make the "bed" slide :)

My sketches so far are drawn with the bed moving and the gantry providing the feet for the whole thing to sit on. This isn't based on anything other than the way I see my build going together based on dozens of different designs that I have seen. I can't work out any pro's and con's other than a moving gantry will take up less space?

Are there any general rules/pointers on this?

Thanks again
Paul