Exporting NiTriStrips creates excess triangles

[pacific-breeze]

I'm using displacement to add detail to rock meshes in FNV in Blender, with 0.1.1 version of the plugin. I subdivide the mesh and then decimate it, exporting to NiTriStrips.
The exported mesh has a very high number of triangles: 7k vertices with 45k triangles. Whereas a 7k vertices mesh would normally have around 20k triangles.
It seems that the changed topology in some way leads to the creation of the excess triangles.

What I did to reproduce:
Open a mesh with 7k vertices, 20k triangles, displace and subdivide, then decimate back to 7k vertices. General shape remains, the displace only adds finer detail. Export using stripify creates a mesh with 45k triangles

Found an easier way:
Import nvn_cliffcanyonl01_frosted.nif and export without any change. Doubles the number of triangles from 6000 to 12000