I have a DIY build in process. Have the RRA Ambi Star Safety and a Spikes stripped lower. The RRS Ambi Star Safety sticks out on each side of the receiver, I think is excessive. So much that if I push on the safety on the right side of the receiver, the left side almost clears the stamped stop on the left side of the receiver. Is there some Gunsmithing technique that I can do to narrow the ambi selector?
Does the positioning of the groove for the detent on the right side of the safety prevent any narrowing process?

I have the RRA star safety on my LAR-8 and like the way it feels. That why I bought it for this AR-15 build.

Did you push the two sides together all the way before tightening the set screw?  On the two that I installed, I used pliers similar to channel locks (protected surfaces of course) to squeeze both halves together as far as they would go before tightening the set screw.  Another possibility is that the lower reciever could be on the thin side of the tolerances.  As long as one side catches a stop, then it should function ok.

Howdy,
I haven't tried channel locks, but will give it try.
I did notice that the ambi side stem looks like it is sticking out beyond the safety stem that it goes into.
I'd like to submit a pic, but dont know how.

Until you have the safety detent and spring installed along with the grip, it will appear that there is extra space on both sides of the ambi lever.  Once everything is together properly, you won't notice it.