LOL VERY long drawn-out process.

The customizer allows you to take any head, neck, and eye geometry and turn it into a set of files that are compatible with FaceGen Modeler.

However, the conversion process is not for the faint of heart. It's tedious and time consuming.

BASIC steps, in order to create a version of a head that works with existing morphs is as follows:

PART 1 -- CHANGE THE UVs of the Head and Neck

(1) Remap head so that no UVs overlap, and assign to a SINGLE material name. This means rearranging all head polygons on a single texture map (instead of multiples as they are now), and the multiple material names will go away as well.  In the case of V4, there are some head parts on the torso body map as well.

(2) You shouldn't have to change the UVs on the neck.

(3) Change the UVs of the left and right eye so that their layouts do not overlap, and assign left eye one material and right eye one material.

PART 2 - MORPH THE HEAD AND NECK TO CONFORM TO THE GUIDE HEAD

Customizer comes with a guide head that it compares your head to as the starting shape. It's HUGE in comparison to Poser figures, and it's also laying down on the floor. You have to rotate and scale the head to place it in the same approximate size and scale of the Poser head. THEN you have to morph the Poser figure's head to match as closely as possible to this head shape. It's important to match it as closely as possible, otherwise your results won't be real accurate for morph or texture results.

Now, the hard part is, the neckline is very much different than those we have in Poser figures. What I've been doing is using the figure's built-in morphs to get feature placement as close as possible, and then completing the morph in an external program. A LOT OF CARE has to be taken to make sure that the vertex order doesn't change in this process. Otherwise, you lose the ability to use the heads as a morph target later on.

PART 3 - Import all parts into the Customizer and follow the wizard. The steps in the Customizer are pretty self-explanatory.  Well sort of. To explain them at this point won't make a lot of sense, but if you have the Customizer and want some input I'll be glad to share

A BIG CAVEAT, though.  The only downside to this is that it takes 10-20 hours to generate the cache data that relates YOUR head to the base head. It takes about 8 hours or so on a Dell XPS Dual Core 2 processor, your mileage may vary. And, if you learn after the entire process is finished that your faces don't line up properly or create good character morphs, guess what? You repeat the process all over again.

UPSIDE ... Once you complete the process, you have a head that you can use in FaceGen Modeler, to create an infinite amount of characters with. AND, if you are fortunate enough to do it without breaking the vertex order, you can use the original figure morphs in combination with the FaceGen morphs to create a figure. FaceGen gets the basic head and neck shape, and you can tweak with original figure morphs.

Now that I've totally bored everyone ... LMAO

I will stress, though, that the process of making a model FaceGen compatible is not for the weak at heart. If you are anal about UVs and vertex orders and waiting endless hours to see if things are working right, go for it!