Hi BOAC,
Does the software mod direct the FMC to target selected altitude rather than any other convenient number?
As far as I'm aware - No. It would have been necessary to reprogram the FDs with Open Descent etc. to reacquire the FL they had departed from.
The first line of the Memory items of the "Unreliable speed Indication / ADR Check Proc"
AP/FD .... Off
was never accomplished. It doesn't help to solve the problem when the FDs keep reappearing with erroneous guidance.