Drop the "1" folder contained within into your install directory. Make backups beforehand.
Affects the model of all the backpack wearing outfits.
Also affects some outfit textures as I had to move the baked in shadow on them.
Included is the TR1 abs texture made by jirazfukko seen here https://www.nexusmods.com/tombraidertrilogyremastered/mods/186
Shadow tweaked on that and included here with permission.
Braid shown in screenshot is from here https://www.nexusmods.com/tombraidertrilogyremastered/mods/158