I totally agree with Larry and the subsequent contributions and hasten to point out that I mentioned that Dr Joe only did some development with the split single, for his own EMCs.
Now I do support Larry's remarks about Walter Kaaden. His theories and positive development on the gas Harmonics now found to be so critical for IC engines, particularly two-strokes, have enabled them to give out their best. Pity we did not have reed valves and variable exhaust port valves around then. My 1951 CycleMaster has a neat little rotary induction valve.

Variable length exhaust pipes and wider use of fuel injection may help to keep the two-strokes in fashion a bit longer.