I am working on making a Surfacing Cover, this cover has a chamfer on it that is not simple. I decided to make it with two boundary surfaces and then trim the extra off although i cant seem to get the trim to work. I've extended the surface so that it goes through the surface i want to trim but still no luck. i have even tried to trim with the

3-d sketch i used with the Boundary surface but i get an error that says my 3-d sketch segments are not coincident to the surface i'm trimming. but i cant seem to find where it isn't on the same surface.

my question is can anyone find a solution to this road block? or is there a better way to make the chamfer that i need?