I made a follow-up call today and talked with Jeff at Mototassinari.
My question? "Will the DF II give better low end performance than the DF III, given that the DF III will have a 'fixed' tension setting?".
His response? "The DF III mold for the KDX hasn't even been made yet. It probably won't be available until next spring. But since it is a woods bike, the reed petals will be selected with that in mind (lighter?), and the design takes into account low-end need."
I think he said that the new DF III is a four-petal system, and I took his comments to mean that he doesn't think there will be any low-end loss in the new design. But in response to my question, "Should I wait for the DF III?" he said, "The DF II works really well in the KDX. I'd go with it now".
So I thought I'd give those of you who are interested an update. The loss of a "low" tension setting doesn't necessarily mean less low-end performance...necessarily!