My BPPC SCSI wasn't able to permanently save the synchron mode for some reason. I ended up using unitcontrol from startup-sequence to enable it.
You could try using unitcontrol from commandline:
unitcontrol DEVICE cybscsi.device UNIT PERIOD 10 OFFSET 8
...or whatever values you want to try. When you find the best (fastest) settings you can add the command to user-startup (or commands if you have multiple HDDs).
It's a bit bruteforce approach, but it did the trick for me.
[EDIT]Ahh, I just reread the post and can see you actually are able to get it going by forcing the mode. Ohwell, then you can just use that instead of the commandline mess.[/EDIT]
