Phase shunts above 16S is difficult. 18S is about the max. Reason: The shunt amplifiers are not rated higher. INA240 can handle 18s but that is borderline and personally I would not operate it beyond 16S. That part is also unobtanium since ages.
The only other alternative is the AD8418 and that part is also not easy to purchase in volumes. Each ESC needs 3 of these.
So low side shunt designs are easier and cheaper to produce. There is more part availability and the parts are cheaper.
For sHFI the voltage tuning is important. It also depends on the motor Lq-Ld difference value.
I will try to make instructions on tuning soon.
FW issues for third party HW should be addressed with the company offering the HW. Vedder is not coding that FW. He recieves pull requests and integrates the FWs.