How to model a morph using a pose?

ttmmttmmttmm

I am attempting to create a morph that better shows the neck tendons when posing the head looing far to the side - to achieve a more realistic look.

Problem is, once I model based on the pose, when importing with MLP, the dial insists on changing all the other vertices as well.

But modeling on the zero pose is really difficult because I can't tell how exactly my vertex position deltas need to be set for the right looking result.

 

I tried to set/unset "reverse deformations" in the import settings, but that doesn't really give me the right result.

agent unawares

Reverse deformation should give you exactly the right result. If you export a character in a pose, sculpt a morph, then load that morph onto the posed character with reverse deformations set, the posed figure with the morphs should be the same vertex for vertex as your sculpt. What process are you using?