I finally tried the Columbia Forest Products mdf core ply. The 1/4 Red Oak cuts like butter with thick proofgrade settings – I increased the speed by about 10 to reduce the tiny bit of char.
Lesson learned - Finish the plywood first, then mask.
Gotcha - This particular CFP ply only has the named veneer on one side, the 2nd side appears to be good quality birch. Big surprise if one is expecting the obverse and reverse to be the same, a la proofgrade. As others have pointed out, CFP has other products that have the named veneer on both faces. I ordered the wrong stuff, hence my surprise.