I would say the back. The primaris look alot like the deathwatch armor to me, so I would just copy that asthetic.
Thanks for the feedback! I think I will probably stick to the back as well. It seems to fit the best in that location.
Combat Sgt is mostly done after a little bit of converting. I started with one of the LTs from the Dark Imperium box:
I didn't like his pose... I felt like he was taking up too much space and was just flailing about. I tried cutting his arm up to reposition but nothing was working. After some thinking and tial and error I decided to swap his Power Sword to a Reiver arm and use a Reiver Bolt Pistol arm. I like the Reiver pistols a lot more and this gave me a more dynamic pose that kept the arms around the body... which is what you usually want if your in CQB.
Too me he looks like he is about to cut his enemy in half with a brutal sweep of his sword:
I pinned the sword and hilt to either side of a small pin i drilled through the hand for stability (sorry forgot to take a picture). The right Reiver shoulder doesn't take a pad so that got a bit of shaving and sanding to fit a shoulder pad on it. These pads were place holders for photos. I have some pads from my Calth box that have raised metal edges that I am going to put on him. It makes sense to me that a melee guy would have a little extra protection and these will visually represent that.
I'm still not sure how to represent his rifle. I'm thinking I may just glue it to his base behind him to make it look like he threw it down as he got into close combat.