This is one method but there is no guarantee that the importation will give you a workable G8:

https://www.renderosity.com/forums/threads/2958956/genesis-81-with-morphs-in-poser-12

I do my importation into P11 using DSON and the Genesis 3 Updater, resave a new CR2 into the Library, and then open the file in P12.  Again, this works for me just fine but there is a tremendous amount of work to apply just to get the figure into Poser in a usable condition.  IMHO, it's not worth the effort unless you are willing to spend a considerable amount of time refining the procedure.