You can really tell they are decals in pictures but in person its really not that noticeable. As was just mentioned, printing decals is a tricky thing and even if they were printed onto clear sheets, it would still show, possibly more so. the options are:
1. dont use them
2. cut as close to the lettering as possible and be happy with how they look
3. cut out each letter individually, but christ what a job that would be!!! something I will not attempt and to get the curve right will require a steady hand and a hell of a lot of patience.
4. use sticker type decals but have full white lettering rather than just the outline. I dont know of anyone else that do these screen accurate outline lettering decals. One of the other big names (Im sure most will know who) has stated he cannot do outline lettering. Either way, whatever decal types you use, you will more than likely get the same effect.