Hi Wayne

I have noticed the EPA hypermiler discrepancy between HCH and Prius II also. I'm unsure what the reasons are, but the higher threshold of the Prius II -- despite it being a heavier car is certainly playing a part. In general, I tend to guess that at least some of the tricks that non-Prius cars can easily take advantage of, are built in to a full-hybrid design. ICE off at low speeds is an obvious one; driving with load, another.

As more and more of the general populace buy hybrids (and moderate their usual driving habits less), it will be interesting to see which design does better.