You ware already solve the problem, but I think your previous method is almost correct.
One thing you've missed is sequence of deformation.

You made morph on joint-deformed mesh, but load morph before joint deformation.
Only method for solving this is editing cr2 file.
Select  your two morphs (only bend, and morphed with bend),  move them after
joint channel. With this, 2 morphs will apply AFTER joint deformation.
Set their value to -1, +1, and spawn new morph.
Again, editing cr2 and move new morph to very last of actor channels.

In my little experience, this method worked.
But if you use there modified cr2 in DAZ studio, they will be broken.