I'm not sure which adapter you are using for your Inon lenses, so it's difficult to understand how it works exactly. Can you still shoot with the internal flash or do you need an external strobe with it?
I have used two Inon UCL-165 lenses stacked together and to avoid getting shadows I just move the diffuser to the end of the lenses. In practice this is done by two holes in the diffuser and piece of elastic string.
The UCL-165 has twice the magnification of the UCL-330, which is what you need if you are doing macro.
This is because minimum focus distance with the 330 is 10cm and with the 165 is 6cm, so you can focus much closer with the 165 you get more magnification.
That was fast!!
I can use the internal flash.
It looks like thisone but without the screw: