Chuck,
Actually with this design, the front diffuser is a must. Without it the light won't shine all the way around the ring causing the bottom to be darker. My first two prototypes were open faced and would not give out an even spill of light. As soon as I put the diffuser on the face, BINGO! it worked. The diffuser allows the light to bounce and reflect inside and carry the light all the way around the ring. I scratched my head for many days trying to figure out why the first two didn't work properly until I taped a piece of paper over it to shoot through.
Thanks,
Matt