Using diopters like cmc or the subsee is near useless with the 30mm macro.... for what I test with Panasonic 30 or Olympus 30, with the cmc you get less or same magnification than the 30 alone.... same with canon 60mm+diopters... most of the power of wet diopters is the reduced working distance.... but the panoly 30mm have already a tiny working distance...
not my experience... I get 2x the dimension as with the lens alone.
its real that the oly 30mm isn't really close to the glass with the 45 macro port.... but not so far away.... the pana 30mm it's 4mm longer and it's close to the glass.... the results are similar.... i own both lenses... ;-)
sorry I did not specify that the 30mm I used ... it is the Panasonic one and it fits well as you mentioned.