Getting even closer with the 60 mm

I have the Nikkor 60 mm, wich focusses already real close, but I want to get closer.

What is the way to go: use of a diopter or use of a Soligor ring between camera and lens (NOT a teleconverter).

The 60mm focuses extremely close already (down to the surface of the port, in my case), so I assume you want to achieve greater magnification, not closer focus.

There's a good discussion going on this topic right now. Check this thread out:

http://wetpixel.com/forums/index.php?showtopic=8924

Oh, thanks