I bought an Eagle Arms (Armalite) complete lower for a great price on the EE. I was gonna use it on my FN A2 build but instead decided to get a McKay lower from Nodak Spud and have Ident engrave the FN logo on it for the FN build.  I had a spare VLTOR FH, DD BCG and ARMS #40 BUIS laying around as well. So...illustrating the danger of having spare parts and lowers around I decided to go with this.
http://www.bravocompanyusa.com/BCM-Standard-14-5-LIGHT-WEIGHT-Upper-Receiver-p/bcm-urg-car-14lw.htm
I've caught the lightweight bug. Shipping the upper to ADCO to perm the VLTOR, then gonna put a KAC M4 RAS on it,maybe an MOE stock. What does the hive think?

I have quite a bit of experience with the RAS and it has always felt like a big chunky block of heavy to me.  I recently switched to a free float tube with modular rails and although the weight is probably similar, it feels much more evenly balanced.  I'd probably go with the MOE handguards.

When is there ever not another build?

True that...BLUE COUCH PICS INC!

I just can't help it!!

JC's couch is to AR's, as the Hugh Hef's bed is to.......well, you get the point.  

Hey JCrowl, how is that MI handgard going for you?  I am about to begin a middie build, and I'm going with one of those again.  Just a thought.  9080 Out

Edit:  Even when you get a new couch, you are gonna have to keep that one, if nothing more than pure nostalgia for photo ops.

Other options for rails that I would check out would be the Rainier Evolution if you want to chop the FSB or Centurion Arms if you don't...both are pretty lightweight.

Sounds cool. I like the RAS myself, but maybe a Troy TRX-E would get you the weight you are looking for.