Maybe it will fit if you remove the rubber in the middle by its width and length + make a square hole (quite big) but the risk of damaging the case is great. It may crack. The safer way is to use pouch. Naked N900 + nanoguard will fit the pouch perfectly. However, the downside is N900 may look little bit ugly. Alternative product would be signal booster sticker. This one is really thin as paper. You put it near the inner antenna of the phone. I did try this on my previous 5800 Express Music. It makes the phone hotter and hang/restart quite often. I wouldn't recommend this.