Olympus Ring Flash Question

[SkinHead]

Hi all,
Before jumping into serious macro work, I have a question re the SRF-11 ring flash system. The product description says it's only compatible with the 35mm and 50mm macro lenses. Has anyone have any experience with other macro lenses, like the Sigma 105mm, which i have?
Thanks

[photo_owl]

the compatability referes to the flash mounting only - so it's down to your diy skills!

as an example I use it with the OM bellows with 3 dabs of hot melt glue (it peels off again when I have finished.

for your lenses the obvious solution is a cheap chunky filter of the right size for the lens - chuck the glass and find a way to connect the flash ring to the filter frame. What you can do is add lobes to the filter frame so that the flash twist clicks into place as it would mounting direct to the 50-200 or 14-54 (it goes on the lens hood lugs)