Yes, I did try toggling between pen pressure fro brush size, but it didn't seem to make a difference.
Sending the config in the overlay section did set the values, but that was just for the overlay. on a bare "paintbrush mode" morph, I experience similar or nearly the same behavior as with an overlay, where it's jittery. This is over USB not bluetooth, mind you. Over bluetooth I'm having detection issues.
Over USB, in the visualizer, I can replicate the behavior with any brush, hard or soft, and see that the tracking is indeed wavering in the pickup. With even pressure applied, I can watch the detection heat jump around and get randomly wider and narrower with each stroke. So it's as if it's not properly reading input.
Furthermore -- with bluetooth: when I take a look at Bluetooth Explorer (OS X Dev kit) and watch the console logging, I see a TON of read errors for the Sensel. I can provide examples, but I was poking around in there to try and figure out the objectclass for displaying battery health or percentage in the menu. Based on the console log errors and the behavior it's describing in the bluetooth logging, it appears as though Sensel is being categorized as an Audio device.
FWIW: My specs are macOS Sierra 10.12.5, Adobe Photoshop CS6 v13.0 x64 bit.