Since March I have been working on a dedicated board to contain the whole system.  Here is the link to the OSH park board

https://oshpark.com/shared_projects/JiEvGsBk

Caution - the output stage produces 80 volt peak to peak which is dangerous, but also within specs for the sonar transducer.

Improvements

• This board has improved power supply decoupling and less ripple.
• It has an input for 5v power to supply the current for the 40volt internal step up supply.
• Microphone holes in the board are better and solder pattern better match specs
• Microphone holes are 2.7mm apart
• High accuracy clock
• Complete self-contained board.

Issues

• Minor amount of noise on the transducer output - sounds like noise from the MCU.   Likely routing issue- capacitive coupled analog input close to digital output.  Does not seem to affect performance.