Thanks all for contributing to my education. Much to think about.
Even with memory "on chip" these days for SOC, it seems IC (MonoMorphic)
+ PIC (PolyMorphic) win over copy-down based on CPU cache locality.
For MegaMorphic case, one _might_ profitably specialize such selectors
to contain/point-to caching dict of class->method as the lookups fault
in. Have to test to see if caching the larger number of lookup results
to avoid chronic dynamic lookup pays off. Simpler cache strategy to
manage than copy-down, but equivalent based on Vanessa's squint test.
Probably data dependent..