I realised (soon after building my third 6MIX), that I needed more than 3 stereo channels, so decided to look for a 4 channel stereo mixer. Befaco recently released the STMix as DIY, and it seemed to fit the bill, so I grabbed the bits.
Was a very quick build, done in about half an hour.
What I only realised after deciding to build the STMix was that this is FAR better than I initially thought. The STMix hooks directly into the master out of the Hexmix, using a cable round the back and also includes a fifth auxiliary channel. This means I can have 5 stereo channels going straight into my master mix (via the ST) and every channel on the Hexmix can have its own 3 channel submix via my 3 6MIXes!
So I now have 18 mono channels and 5 stereo channels going into the main mix, then out via a stereo compressor (Disting mk4). 28 channel mix bus ?