How to downgrade:
1. Make a backup of your current servo firmware and save it to your local drive
2. Make a second copy of that backup file as you are going to edit it and you might want to keep the original firmware file untouched
3. edit the firmware file with an editor and find the version number, line 7 and following in my file
"External Version
TRUE
1
15
4
7
5568
N"
4. Change that to something lower than the current firmware for the legacy devices (currently 5.6.1.253, so changing these lines to for example 5.6.0.252 as shown below
"External Version
TRUE
1
5
6
0
252
N"
Make sure you only edit the numbers and to keep the whitespaces before and after where they exist
5. Save the changes and use the restore backup firmware functionality to upload that firmware to your device (worked for me but no guarantee that you won't brick your servos)
6. The same firmware as previously is now installed but the Dynon tool will detect the servos having an older firmware and will allow you to "update" to the latest firmware for the legacy devices - which in fact downgrades them
7. After successful downgrading make another firmware backup of your device so that you have a valid backup file of the latest firmware with the right version number, you can view that file with an editor again to verify your success
I downgraded two SV32 servos using that method and they both work fine with my D100 and v5.6.1
