i have the same board in my amps. and i was told they are the exact same board by the nendo repair guy. so i trust his word. i got 2800w@5 ohms from my amps on 18v, yes 5 ohms. from half ohm rising to 2.2 ohms on 18v starting voltage dropping to 17.4v i got 5742w@2.2 ohms.
with your rise form...