One being modifying the cushion that pushes against your face. If you make it thinner, you get a better fov from being closer to the screen.
Honestly, you're going to get a lot more information from google rather than here. VR still isnt big enough to have a massive following here on OCUK and you might be waiting for days for stuff you can find via a search engine.
Its a bit worrying that you're asking these sorts of questions after you've bought one tbh.