I wonder if the pressure graphs from two of these

http://www.optrand.com/fliers/psiplug_%20060201.pdf

Indexed 180 degrees apart
in similar cylinders
could determine if indexing
speeds up combustion.

After a first run
the two spark plugs could be swapped
and a run repeated.

Dual plug Hemis
Seem like they might offer
further test possibilities
but i cant think of how to best do that yet.