Left: M42->M42 helicoid + μ4/3->E adapter (glued without any filing)
Right: 42->49 step up ring + EOS->4/3 (glued together after filing the both)
I already have F->M42 tube, see > http://www.pbase.com/image/124972053

The both together make an EF->E adapter with a helicoid of 9mm extension, and
also you can make another (right side) heads for Minolta SR or Canon FD mounts
if you wish. Of course this adapter can allow to focus infinity without a problem.
The reason I made this adapter with a helicoid is this; when I have an FF NEX(?!),
the most of lenses can be used with near focus ability regardless their focal length.