Thanks for the follow up on the plane. I, in fact, did use my powered jointer to flatten mine, so I know it can be done. Just go lightly and watch out on the mouth. Hopefully that “depression at the centre” can be used to your advantage. Maybe you can get all of the flattening that you need before you start chewing on the mouth area.
I set my jointer for 1/64th—1/32th cut and snuck up on it. Mine was twisted as well, so I had to be very careful in not rocking the HP across the jointer. Best of luck on this. Got my fingers crossed… ;-)