Lowering the main table until it kissed the top of the Powerpro did the trick. It gave me about 1/8 to 1/4 more clearance and the board progressed through.
I think the kickback pawls (thanks for the vocab!) were stopping the forward motion while pushing on the board, as someone adroitly noticed-they were all the way up riding in their slots.
I did get some slight burning on about 25% of the face, so i think next time I will try a 2 pass covered approach. It did get a little awkward once the board was fully under the plastic shield and trying to push through the narrow gap with the push stick.
As I run the saw with the quill pulled back, the main table interferes with the top of the powerpro, but I was wondering, is it OK to extend the quill out 3 or 4" to allow the table to come down further, or should the table saw only be run with the quill near fully retracted?