Quote Originally Posted by Sterob View Post
Good point..... 'Complexity and Less Overhang' verses 'Simplicity and more Overhang'...
If you have access to a milling machine I would definitely put them top and bottom. If you want to mount them on the face and keep the same rail separation then you need a deeper gantry, if you use 160x80 profile for the gantry then the Y rail centres will *only* be 120mm apart (distance between outermost slots), the same profile with top-bottom mounts gets you ~180mm centres. On my last machine I used 160mm ali box section for the gantry and with face mounting close to the edges got around 140mm centres.