I think it's coming along nicely!
When it comes to coloring, the CRL is pretty open and simply calls for armor that "Must be painted a metallic grey that is weathered in a pattern consistent with the rest of the armor." My personal preferences is for a darker metallic gray, but I have seen great looking acolytes that are both on the lighter and darker side.
Regarding the center piece of the abdomen- the reference image does show that it is a darker color. But in my opinion the two hues are closer in value than in the picture you posted above. In the reference image below it appears that the abdomen is a dark grey and the center of it closer to black. In the image you posted the abdomen is more of a bright grey and the center part close to black.
Of course, one thing that makes this even trickier is lighting... the abdomen armor you posted above may actually be darker in most real-life settings than it appears in the photograph.