[pillowmeto]

Do you know of any published SAE papers on the subject? I did a search and came up empty handed.

I would think that a gentle slope over the roof of the chamber leading to a final concentrated expulsion of the gases would be more effective.

The company I work for has a in piston design using a gas chamber inside the body of the piston connected to the combustion chamber by a small port that has great result on fuel consumption and emissions. Some of these small changes have great effects on combustion.