The first thing that stands out to me is the overlap in the back. There should be little to no overlap between the back plate and kidney plate. I think this can be accomplish by doing two things: 1)Bring the back up a little bit - not by much, but you have a little room there, and 2) trim a little off the top and the bottom of the back plate. To give you can idea, here is Apok's Nova:
I would definitely connect the sides of the chest plate to the back plate to hold them in place.
Your belt is a bit off centered and sagging a little. How do you have it connected on the sides? - Just saw the pick above where you have everything laid out and I see its not attached to to the ab armor. You can connect the ends of the belt proper to ab armor which will help keep it tight and in place.
You mentioned to me your ab was dropping. Sounds like an elastic issue. I highly recommend replacing the ab to kidney connector with adjustable suspenders.
Do you have a heat gun? It is hard to tell, but it looks like your ab chest and back plate, where they hit the shoulder straps, could be contoured a bit more. That will help with how the armor sits. I didn't own before I started armoring, but it is one of my best friends now.
Another recommendation, but not required, is to reshape the chest plate. This is a good tutorial for it. Really makes a nice look.
Most of what I mentioned likely wouldn't hold up approval. The only thing I mentioned that is specific to the crl's is the back/kindey overlap. You did a great job Nicholae!