hello,
I do not know if you need the information anymore, because no one replied very much.
but here is my information:
first of all, which one do you want to make??
this one:
or this version??:
I have a shadow guard costume which looks like the second version.
I know for sure that my version has no armor at all, the only things that my shadow guard does have are: boots, a helmet, long black leather cloves, a (self made) lance (also called a saber pike/staff) and 2 robes.
the shadow guard on the first picture is something very different, because he does have armor, but he doesn't have any robes except for around his waist.
also his armor looks like some other characters from the star wars movies, such like a stormtrooper and a imperial officer.
and to answer your question: yes this version has a backplate that looks like something between the one of boba fett and the one of a stormtrooper.
as for the saber pike/staff I don't know very much about that, because mine does not look like these versions very much.
but I think I am going to make a new one

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but maybe this will help you out:
I hope my information will help you a bit

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If you have any questions, feel free to ask

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greetings
Marielle