Sassan,
I managed to pick up a used DG-2 eyepiece magnifier but now have to wait for the eyepiece adaptor to arrive.
Now I just need to find a decent 1.4 converter that will work with my 400mm f5.6 AIS lens. A look at Andys lens comparison suggests I need an old 500mm to go with it on the basis that a 500 is a lot more portable than a 600.
Don