Don't forget to collect also the plunger rotation over rod position...

Your thoughts about flame front is correct, but (at least in my opinion) not worth and hardly possible at all to calculate.
What I intend to do is to measure the pressure curve over engine crank shaft position. This will give information about the pressure build up, timing and duration of pressure/flame runtime/injection.
There are many parameters such as spray time and pattern and the whole thing with pressure waves in the hard lines.

Tom