Finally had time for more tinkering. Sorry for the long pause but 'work' does pay the bills! LOL

I ordered a prop hub, velocity stack, and resistor spark plug from Carr.
In the meantime I disassembled the engine completely. What I saw is indicative of restricted exhaust and/or low CR (compression ratio).
Future mods may include opening the exhaust port depending on the timing and removing the intake restriction.