I'll preface the attached .nif file by saying it is ham-fisted ghetto creation as I have nearly 0 outfit studio capabilities. It has some very visible stretching/oddities on the lower rack. I'd imagine hdt settings and tit size in race menu can cause some weirdness as well. This is only for max weight.
As far as making your own abomination and expanding on what was said above:
Create a body with your upper rack and save that preset. Copy the .nif it makes somewhere else because your lower rack is going to overwrite the file when you make it.
Create a body with your lower rack and save that preset. Copy the .nif it makes somewhere else.
I wouldn't change anything besides the tits or you will probably get more deformations.
Save the presets because you will want to come back and fiddle with the heights/sizes/spacing.
Open outfit studio
File - > load reference the .nif file in the slider set xml file path for the upper rack
File -> load outfit the .nif file for your lower rack
Right click on the base shape reference body under the meshes tab and duplicate the shape (give it any name)
You should now have two parts under new outfit drop down menu.
(if you hide the base shape both racks should still be visable)
File -> export current -> export .nif
And that should be it.
femalebody_1.nif
