Solution found.
It turns out MipMaps were my issue. Turning them down to 1 within OpenIV has given me crisp textures.
Hopefully this helps someone else having the same issue.
Okay this is bound to seem like a stupid question, however it has to be done.
I'm currently creating skins at 4K (4096x4096). However in game they're clearly not 4K and appear to be at 2K.
Is this simply because of my in game resolution? Would these skins show up correctly for those running at a high enough resolution?
Thanks.