ProBuilder Auto UV creates larger Mesh vertices than original model

Anyone have a work around for this? The model looks exactly the same, but the vertices expand by more than double after I call import. This is what I'm using to import the mesh:

Code (CSharp):

1.  
2.         var importer = new MeshImporter(objectToProbuilderize.gameObject);
3.         importer.Import();
4.  

I think the issue appears when I try to fix the UVMap, this is where it creates more vertices:

Code (CSharp):

1.  
2.                     AutoUnwrapSettings setting = new AutoUnwrapSettings();
3.                     setting.fill = AutoUnwrapSettings.Fill.Tile;
4.                     setting.anchor = AutoUnwrapSettings.Anchor.None;
5.                     setting.offset = Vector2.zero;
6.                     setting.useWorldSpace = true;
7.                     setting.scale = Vector2.one;
8.                     foreach (Face F in pb_mesh.faces)
9.                     {
10.                         F.manualUV = false;
11.                         //F.textureGroup = 1;
12.                         F.uv = setting;
13.                     }
14.                     pb_mesh.ToMesh();
15.                     pb_mesh.Refresh();

Preferably there's a way to create the ProBuilderMesh/Fix UVS and keep the same Mesh Data.