These steps (short version) work best for me:
1. Import the MakeHuman character (best height: 185cm) with the opensim-rig (26 bones) to blender
2. Use the Avastar Transfer-Tool, choose Extended Rig, Repair Rig
3. Unbind from armature, delete the skeleton
4. Alter the location of the meshes (eyes and so on too) slightly (0.015) and apply
5, Add new Rig, extended-only rig
3. Go to the Appearence-Tab, select 'skeleton' and shorten the neck length (and the hands too, but that is another project), best for me to 34, so that the face-bones are in place.
4. Set bind pose and bind to armature (bones).
5. Export with Avastar
Yes, I made animations too, but this is not that easy, because teeth and tongue have to be weighted manually.