Still wondering why no return edges? Yeah, that is something a lot of us asked when building our first suit. The simple answer is that the armor seen on screen had no return edge. Here are some examples:
Link to gallery: https://www.whitearmor.net/forum/gallery/category/24-anh-tk-reference/
And I found that most things like this no one will notice besides other troopers. Whether you have an edge or not in the end is up to you. You can always come back later and trim it. With that said, I am a fan of no trim.
Hope this helps.