Good morning Raestro, I just watched a video on how to change the Shells and it did talk about towards the end of the first video you sometimes need to trim some of the plastic with an exacto knife from which the way the plastic is molded. Also it shows the importance of putting all the ribbon cables back the correct way to ensure a correct fit. It's a good video. Here is the link to watch it. I hope it helps. Please let me know, Thanks, John
http://www.instructables.com/id/How-to-repair-your-Nintendo-DSs-shingle/