I can see either a dome or a cone for a diesel head working correctly but I would think if you ARE going to include a squish band it should have some angle to cause the swirl. It was determined in glow engines long ago that some angle was needed for best performance.
Might the use of a squish band be better for larger engines but not necessarily for smaller ones? Is it possible that the squish area will fire first or cause a more complete combustion on a diesel?
Hobbsy, do you still have that head? Could you add an angle to it and see if it runs cooler?

Geez, I seem to have a lot of questions and comments, but no answers...sorry.

George