A while ago someone posted a VR mod using UABEA. I decided to see if I could change the min/max breast size using the same tool since I saw some complaints about it.
On v.39R3 I managed to change the slider min/max, which also changes the main menu model. Unfortunately in-game it doesn't seem to affect the minimum and the maximum just makes her boobs wider. I think it will require editing of the bones/morphs in some way which I don't have the time or patience to reverse engineer. There's a small possibility that the game loader doesn't use the slider value for all scaling aspects and could be modified to use it, but I doubt it.
For anyone else interested in continuing this work, open data.unity3d in UABEA, select level1 from the dropdown, click Info. View>Filter>deselect all except monobehavior.
Find Path ID 83013 or search by name "Slider" (how I found it originally) and open each one until you see the values 20 and 95. View Data to view the data and Edit Data to change the min/max to what you want. I tried as low as -100 and as high as 800. The Path ID might change in different game versions so that's why I included the long process for finding it.
File>Save and after that finishes close that window and File>Save in the main window, make sure to backup your data file. I didn't exactly follow the VR mod's instructions so maybe doing the whole save as a different name and rename might matter? Feel free to experiment.
If you're using AssetRipper then extract everything and look under Assets/6 - Scenes/LoadedScenes/MainMenuScene.unity. This file is a nightmare. Search for "--- !u!114 &83013" on line 23171344. I did not find Jiggle Slider in the file but I did see it when I opened the scene in Unity, it should have a min/max of -.4 and .4 with a default of 0.
And now a small rant / constructive criticism on this game's model. Her boobs look like two coconut halves glued to her chest. Look at Skyrim models, CBBE and UNP scale really well, there's mountain-size tits shaped better than this. I know the VS dev doesn't read this thread but bro go ask for help from one of those model creators. I'm talking about improving the model's technical design and structure, obviously I don't expect you to port nifs to Unity.
If it's already on your radar to improve then great, I don't want to come across as angry or demanding (or a better designer. I can't make models for shit). Gameplay improvements are far more important than the model.