Hi dugal,
yes the countersink suggestion came also to my mind, i'll try to model this in the next revision. from a mechanical point of view, this is kinda hard to accomplish, because the gap from screw to side panel is quite small so one has to take care of not to break the wood apart (build out of mdf in german).
the inner ring cut in the aluminium plate is designed to act as a volume indicator, as just suggested

i think the material chosen for the diffusor behind the alumium is not yet satisfiing, next revision is gonna get a more realistic one.
anyone modelled a simple led lightsource? i'd like to compare it to mine
