Bad news :(
Nice print, nice design, bad functionality..... tested it by talking and walking around it, the sound from the back seems just as loud as sound from the front.
I'll have a look at external mic's. At least the good thing is I now have a good model of a perfectly fitting "frame" if I want to design one later for mounting an external mic...
Maybe as a last try I need to test it out in the open... as the sound is really dampend when you put a finger on the mic holes.... so theoretically it should have some effect...