TBH idk why you weren't more careful having already broken the first one. The guide has clear pic of where you should cut, so you have to be careful NOT to go inside that line unless you plan to relocate more stuff. If you take your time by triple check the lines your drawing and carefully cutting slightly outside the line, you really shouldn't have any issues. Judging by these past two wii's though, I'm gonna have to take a wild guess and say you rushed with your cut. You just have to be more careful considering the trim is perhaps the most important part to a wii portable.