For the OP, here is how a kidney grille looks with silver+chrome vertical bars:
(I found the pics on a german forum)

 

It was a custom job

 

 

I think this looks really good. I havent seen anyone do this before. Can you just install the factory slats in the matte grills?

 

I think this can be done rather easily.
I was planning of doing it today, but unfortunately the the wrong part was picked for my order and I have to wait till Thursday before I get a shot at it
But Gloss/Matt black ring and the factory chrome bars sounds nice to me.

 

yes i got my matte grill and was going to put the chrome bars in the black frame but i changed my mind when i snapped a clip. my luck i woulda snapped all of them. but the oewm kidney is 2 peices so if ur aftermarket is 2 peices they should be interchangable

 

I just bought the original black ones from BMW. Should be fine for me.
They actually come in 3 types here in holland:
1. All black
2. Chrome ring, black bars
3. chrome ring, chrome bars

Missing is the Black rings with Chrome bars, so it will all be falling back on handy me

BTW, I always soak in hot water for a while to soften the plastic a bit. less likely to break. I think a heatgun could do as well, but that increases chances of discoloration.
Breaking parts during modding is a bitch