Hi Keith,
First what a masterpiece of an engine does you build! I am new here on this forum, working on a one cilinder project.
I saw that you have plans to change the valve timing. Maybe I could help you with some theoretic/simulation things. At school I've acces to a powerful Internal combustion simulation program, called GT Power. If you want I could do a couple of models with different valve timing etc. With proper inputs and specs of the engine it is possible to see lots of data, for example the fuel distribution over the cilinders or torque/power. It could give a idea what could be going on in the engine.
Maybe you could use the next info. In the book of Richard Stone, they advised specs for a valve timing as follow:
Intake opening: 10-50 degrees bTDC
closing: 40-80 degrees aBDC
Exhaust opening: 40-80 degrees bBDC
closing: 10-50 degrees aTDC
And the degree from TDC to max lift intake and exhaust between 104-109 degrees for low-mid range engines.
I added a picture for explain the numbers more clearly.
Greets Alex