Narrow mounting, yes I had just been thinking that. I'll wait and see what Ross thinks. I could separate them a bit more if I make the axis wider but I don't really want to sacrifice the Y travel. At the moment the travels are 1700x740x400 (XYZ).

Adding the L section to the previous design is perfectly possible so I may well do that. Do you think if I did I could use 15mm aluminium plate instead of 20mm for the bit they mount on?