PT6's most accurate oil level is when it is checked within 10 minutes of shutdown.

I'm guessing Jungle owns a C310-R. I love those planes(only flew 2000 hrs in them at my last job). You actually own a FIKI model, or 'full-deice?' I'm suprised the 9 quarts was too much, in our fleet(9 R-models) we'd usually go around 9-10qts and be fine.

As far as any engine in general, I believe whatever its "Max" value is, is the engine can usually run on 50% of that for certification purposes. Funny how it all works in the end.

How I usually manage oil levels, I usually fill for normal 1-3hr flight 75% of the max level, and I'll go +1 qt. for longer flights just to cover myself if I don't know that specific aircraft.