Thanks for the chat Black Elk ^.^ I feel as though it sounds like you've studied this area in more serious depth than I have - I've only studied it in passing, as an interest and never as a dedicated endeavour, so I welcome someone more knowledgeable ^.^
It was a toss up for me - art standards treat 1:8 as the golden ratio, but "real world humans" average from about 7-8 (with other extreme outliers as well), with ~7.5 being the more realistic average. So I was debating whether to match to "art standard" or "real world standard", since, well, this IS a work of art after all.
I went with 1:7.5 with my human models in the end, but the actual head *Shape* could probably use a lot of work. I'm not THAT good at this, despite my efforts <.< >.>
Direct scaling the halflings causes some visual ticks that people often complain about - overly scrawny limbs and tiny-seeming heads being the main ones. I felt they looked better with minor adjustments in that area - slight thickening of the limbs in relation to the trunk, slightly sturdier legs, a slightly stockier torso ratio, but only slightly, and then also setting their heads to a 1:6.5 ratio - larger in relation to their bodies, but only by enough to avoid the 'tiny head' impression of the smaller model, or at least that was the goal (The halflings that I posted a while back, in LotRO have substantially non-human proportions, and they actually look *Fantastic* - they look like normal, healthy, believable creatures, but also clearly not human creatures as well). The attempt I've made comes across fine to my eyes as a result of those tweaks (though I continue to tweak it), but my eyes are the only ones I can test on, and I can't say how effective it is for others.