Skyrim Size Textures

[SkyTaylor21]

I'm trying to apply skyrim sise textures to oblivion models. I started with using skyrim's imperial fort textures on oblivion's for textures just to see how skyrim size textures would work. The textures look great but the new textures only seem to work in the construction set. I went in game and the skyrim textures weren't applied to the models like they were in the construction set. The model looked like the original oblivion model with original textures. Does anyone know why this happens?

[SkyTaylor21]

And just to make sure I'm not misunderstood, I would like to point out that I don't want to port skyrim's textures to oblivion, I just want to use textures that are the same size as skyrim's.