My spare time for robotics has been very limited the past five years due to maintaining four different plugins for the Moodle LMS and my wife's two very serious health problems. To make things easier on myself, I have put together a Pi mini tower to hold the boards I am using for development. The mini tower has a Pi4 on the bottom layer, then a Pi3, and on top is the Arbotix Pro.
Click image for larger version. 

Name:	20210131_111810.jpg 
Views:	388 
Size:	116.5 KB 
ID:	7672
After putting it together, I almost immediately removed the clear top so I could easily swap the power leads between the two Pi's.
The Pi3 runs the HROS1-Framework without any problems, as long as I do not upgrade the OS.
When running the framework on the Pi4 there are a few errors generated when compiling the code. I am still working on fixing the communications between the Pi4 and the Arbotix. Send (Pi to AR) seems to work, but I cannot seem to get anything back.
Sadly, due to appointments, I haven't even had time to turn it on for the past four days.