Hi Jonathan,

I've gone for about 80mm spacing between each 40mm extrusion. There will be a cross brace at each end and in the middle.

I think putting HDPE strips on either side of the extrusions seems a good idea. That way I can still use the T nuts and also move the extrusions about to support different size parts. Do you think there is any advantage in using Tufnol, it can be harder wearing I guess.