In most renders, it's not a big deal since this particular part of the body is likely to be hidden by hair.  Still, it's bugging me, so I was wondering if anyone has had a similar problem and might have a few suggestions.

Thanks in advance!

What procedure are you using? i would assume this is a weldsplit. Trymake the neck invisible and observe the vertices. On the seam. Did you modify the neck also or did you only morph/rework the head actor without the neck?

From many experiments with the cylinder artifact, which looks exactly like that, I'd say there is a UV map incongruity, rather than an XYZ coordinate problem.

I find it suspicious that it looks like it occurs on a seam. On a seam, each vertex in the preview is indeed two vertices on the same xyz position, as the parent pos is copied over the child pos to glue the body parts together. However, normal computation near seam have a problem of internally using the old individual child vertex position rather the new value set by the weld operation. Its an "issue" that can be observed down to poser 6, maybe even lower versions. I think it isnt easy to fix. not sure if there are plans to do sth about it. If he morphed the head, then i hope its repairable. For uv issues I do not know.

UV mapping should be easy to check. Unplug everything from the head and change the Difuse Color to something like red, then do the same thing to the neck but change it to blue. If the colors are in the wrong place you will know which material area is causing the problem.

lmk

I could reproduce the problem if I make a morph with pml and use only the head actor for export, but not the neck. Morphing the vertices on the seam causes the weld to split and pml complained about it. The morph brush then created artifacts similar to those observed by scriptor.

i couldnt solve the issue with morph brush, but what looked as if it work was to export neck and head twice, once with the bruised morphs enabled and once without them, and to load this back as a new morph with pml. Then the seam was aligned and the shading ok.

What happens if you export the V4 head and load it into M4 as a morph rather than grafting it on?

Quote - What happens if you export the V4 head and load it into M4 as a morph rather than grafting it on?

That's basically what I did.  I exported the morphed V4 head as an OBJ and loaded it into M4.  I then created a custom morph to smooth the head/neck seam as best I could.  I was using the term "graft" loosely, referring more to the appearance of the result than the actual process.  Sorry if it caused any confusion.

Anyway, this morning I tried exporting the entire morphed figure (M4 with male V4 head) as an OBJ and creating a custom CR2 that uses that OBJ as its base geometry.  This works like a charm as far as the jawline is concerned, but now it insists on skewing the supposedly "zeroed" positions of the thighs and feet towards the default standing position (what you get when you load out-of-the-box M4), even though the OBJ was saved in zero-pose and even appears perfectly zeroed when imported directly into Poser.  Plus, the toes of the CR2 go berserk whenever I pose it.

This is so typical of Poser, LOL!  The solution to one problem only seems to create another.

Quote - now it insists on skewing the supposedly "zeroed" positions of the thighs and feet towards the default standing position

You did remember to turn off IK, and export "As Morph Target"?

Argh!  I've solved the leg problem, but at the same time I noticed that the chest gets screwy if I bend either collar.  Here's M4 with a male V4 head and his left collar bent 15 degrees Front-Back.  I never touched anything below the neck while morphing, so I'm at a loss to understand what's going on here.