WARNING: WHATEVER I DID IN THIS VIDEO (Leaving the camera open and using a razor to carve) IS TOTALLY UNPROFESSIONAL AND NOT RECOMMENDED. IF YOU HAVE A BETTER WAY TO DO THIS, PLEASE DO.
Anyway, one problem I found when connecting my lens on the reverse ring is that the aperture is set to max which requires more light and doesn't give the picture I want (Close up with low aperture).
My solution is to use a spare lens back cap, carve the inside and keep the latch that keeps the aperture open so when I screw it in, it opens up the aperture.
I'm sure I'm not the first neither the last one to come up with this solution, but I haven't done any research for it and came up with it while pooping after having a double cheeseburger (Sharing alot?)