i've seen it done a few times and it is what i'm planning for my first build as i'm only building it to make the parts for my second build.

on my second build i want the rail supported in the upright position not just because it makes more sense in respect to were the load is coming from but also because i imagine the area were the rail joins the support getting completly full of sawdust, chippings, coolant spills and all sorts of other rubbish.