Tony -- I like the chrome above the plate! Like it a lot. I have a chrome piece for my Tahoe sitting in the garage. Haven't gotten around to putting it on yet, mainly because I think that I'll be removing the bowtie, and then sticking it on the chrome piece, so the whole process is going to be a little more involved. But, probably this spring I'll get to it.
As for the position of the "GMC," I can't tell that well from the pics, but I'd say that you should center the logo between the bottom of the piece and the first crease toward the top of the piece. In other words, I think you should center it according to the flat face of the piece, and not the entire piece. That's how I'd do it. Maybe you have it there now -- I just can't really tell from the pics. Need some daytime pics!
Oh -- One more thing regarding the rear of your truck: consider how some aftermarket tail lights will spruce up the rear of your truck. Yes, the Denali tails distinguish the truck from non-Denali Yukons, but I don't think they're the best looking lights out there. If you were to put some G4s on there, they'd spruce up the rear of your truck in a subtle way, I think.