Fixed!
Figured it had to be prop or motor or esc. Changed out all props, no difference.
Checked out Output page in the GCS and BOOM, there it was, Motor 6 was at 60Hz, all others at 490.
EDIT. THIS HAD NOTHING TO DO WITH THE PROBLEM SINCE MOTORS 5&6 ARE ON BANK 5 WHICH WAS SET CORRECTLY AT 490. this kind of mistake happens when learning by doing. I used the LP wizard to setup the hex, hadn't even looked at the Output page 'til today.
I can still hear/see some slight oscillation but I'm guessing this is due to the pids I'm using being developed on the same frame but set up as a quad not a hex. Plus motors and props are different.
At least it flies now
Thanks again for all the help!
EDIT: Cliff, just out of curiosity I tried lowering that filter setting to 42...oscillations came back with a vengeance! Not flyable.
So, then I tried the other end of the scale and set the filter to 256 Hz and, wow, seems to fly beautifully. No more time to play today but didn't hear/see any oscillations during 3 minute test flight.
Rock On. Will report any further developments in this thread.
Would also appreciate help manually setting up OneShot on this Hex.