I've had 3800performance MSP upper square mounts for over 2yrs in my GS but now im leaning towards intense performance poly square mounts. I loved the MSP mounts but I hated the 3 piece design. Intense mounts are 1 piece, so more solid and less chance of any unwanted movement.

And flipped stock mounts are a great idea and less expensive, but i think once you start modding and gaining more power, those poly square mounts will put more power to the ground