I have a Borg #7887 FR/FF and it works perfectly with my full frame Canon 5DH on 80ED, 100ED, 150mm diameter F5 achro and the Tal200k. It is adjustable for different focal lengths by removable spacers between the two optic elements.
here
http://www.sciencecenter.net/hutech/.../html/7887.htm
You will also need the Borg Canon T-ring and nosepiece.
http://www.sciencecenter.net/hutech/.../html/5005.htm
http://www.sciencecenter.net/hutech/.../html/7425.htm
Not cheap but it works.
I would be willing to loan it for tests on anyones scope as I will not be needing it for quite a while. I am going to concentrate on widefields with the 300mm lens.
Bert