Quote - there is a headsize morph, that does the whole job, but i don't know how to convert the morph setting to percentage, so that i can match up conforming headware and hair with the scaling adjustments

That is actually a "MorphForm", which is the term DAZ use for the ERC master dials that manipulate/coordinate an appropriate set of other channels (in this case various scale channels) which may or may not include real morphs.

Quote - and I've found that V4 and M4, when you scale their head, the inner parts in their heads don't scale with their head.  lower jaw, etc is under their head in the heirarchy, i don't understand why it doesn't work.

Sounds like the propagating scale channels aren't present (i.e. were removed and replaced by the various MorphForms). > Quote - I would like to understand what the single axis scaling issue is about (Poser 7).

Assuming that the effect being described by where you picked up the term "single axis scalling issue" from, is the one I think it is, then if you scale the body of a figure in (say) the Y direction, everything is fine until you attempt to pose other actors like arms, which as they move up and down don't behave as you would want them to.
The other scaling problem, is that until a recent P8 SR, conforming items didn't track scale changes.