I've spent a bit of time in the past few weeks optimising and improving performance. For the Arduino expansion boards I've been able to increase the maximum sampling rate by around 40%. I'm slowly doing more work to reduce the amount of serial traffic required as this appears to be the major bottleneck. 

On the hardware front, my prototype RaspberryPi DAQ boards arrived from OSHPark as did all my components, however... DISASTER! Somehow I've got the wrong footprint on the RaspberryPi header. The pin pitch is too small. 

I'd normally consider building one anyway for testing purposes and just using wires to connect the board to the Pi but given the ADC is fairly expensive I don't think I'll do this just yet. In the meantime I'm going to have to do a bit of investigation into why my footprint was wrong.