Trouble cutting a part to create a cover

Hi everyone, I have a part that I created using Lofted Boss/Base which created some unexpected funky curves.  I've attached pictures of my part.  Basically I need to cut the 'roof' off of this part and create a cover (separate part) that matches these curves.  I haven't had any success matching the curves that are on this part by any traditional methods, is there another way I can do this?  

Solidworks3d Contentcentral