Cannot make thong morph/scale with pregnancy belly

[RedPassenger]

I've been trying to figure out how to make a thong piece morph in-game with SoulGem Oven pregnancy belly version. 

In the video I show exactly how I go about converting the thong in Outfit Studio and how it doesn't do what I want it to do in-game. Can someone please HELP ME

Converting Thong Issue Skyrim (youtube link)

[RedPassenger]

SOLUTION:

So I basically struck gold and found dedicated help by 

dint 999 check out his youtube channel btw, lots of Skyrim outfit related content etc. 

https://www.youtube.com/channel/UCgEf43yEvzp6KihO5Xr30HQ

 

The PROBLEM was that 

here it is absolutely imperative that the "Output Data Path" is correct

In the pic it is WRONG because that is the path where I saved my backups and foolishly thought it didn't matter.

It matters because by creating project with the wrong path it also dictates the path which the later created tri. _1/_0.nif files read, and if they aren't in line with what the mod's ESP wants them to read then you get my problem. To quote a more technical explanation by dint 999

Quote

The tri-file must be created together with the mesh 0 and 1 and the file paths must necessarily correspond to the paths specified in CKit in esp
so you have to create a joint .._ 0, .._ 1 and .tri file. If you create a separate tri-file and put it to the previous (old) mesh - this will not work. only joint 3 files