hey,
I understand your problem. Do it my way, I don't own a cnc drill or too.
the mount ist connectet to the diff whith some layers of carbonfiber and glassfiber, some leftovers. glassfiber/gfk is much stiffer than alu, but easy to work with (drill, saw). I glued it together with some good 2k-epoxy. just take some gfk (glass-fiber composite), its bloody cheap. cfk has the better looks, but it 's very hard, that means it "eats" drills and saw blades.
the mount is connected to the chassis as well with a piece of aluminium, the relatively thin quality is easy to handle with normal tools.
this mount is quite "different", but like that it was easy to get it done with my old drill etc. and I have to say, it's stiffer then my other mount for the kb45xl, made of alu. there is no flex at all. and its lightweight.