When it comes to bend relief cuts, this has been the best way I have found as of yet.
Extrude to body, convert to sheet metal under sheet metal menu, add flange, or add bend if you wish to sketch a line on your body (if so create new sketch on body and sketch bend line).
select unfold
create a new sketch on bend profile
find center and sketch construction line.
center rectangle width =kerf width (.05 for me)
finish sketch and extrude bend releif (cut)
refold body.
i made a quick video that may or may not help.
EDIT:
apologies my screen recorder doesnt record pop up windows.
you will not be able to use lead in or out on a releif cut if you use a kerf width as shown for the size of cut.
