For a prehistoric save I'm trying to make the Bigfoot skin into a default replacement for all four Maxis skins. The general idea is to remove the replacements one by one as the generations progress to make more and more hairless mutants appear.

Anyway, I'm following this tutorial. My problem is, the template attached to the tutorial has four files labeled efhairbald, emhairbald, ufhairbald and umhairbald while the Bigfoot skin has hairfiles for all the lifestages plus two blueish files with "alpha" in their name (afhair, amhair, bfmhair, cfmhair, pfmhair, emhair, tmhair, tfhair, amhairalpha3, amhairalpha5). Can someone tell me which file from the original goes where in the template?

If I load my unfinished default replacement into Bodyshop, the sims are missing the backs of their heads when bald and some hairs turn partially black.

I put emhair and efhair into emhairbald and efhairbald and then afhair and amhair into ufhairbald and afhairbald.
Result: The sims with the new defaults now have complete hats and nothing turns black anymore. However, I now feel like in those jokes where it says "some assembly required" and you've got parts (files, in my case) over. So despite me having working skin defaults now I'm still interested in what the correct solution would have been.

If you wanted to split things out, you would have had to replace the TXMTs for those ages/genders to refer to separate texture files, instead of all using the same one. It's sort of similar to how HP made her dependent defaults, here: http://www.modthesims.info/download.php?t=221480

So I take it I didn't do anything wrong per se, just opted for a simpler endresult? I'm mainly worrying that my defaults could damage something in my game or glitch out some day because of the left over files. But if these are only meant to introduce variety between ages and genders (as I gather from your post? as I said, bloody beginner here) I can live without that.

Yes, exactly - what you did is perfectly fine and won't cause any problems, but if you want to make it more complex then you would have to use a more complex method.

Thank you for clarifying this, that being settled I'll start my new 'hood today