The "CheckStop" saw common use in law enforcement, and already was well protected against small arms fire. When converted for military use, instead of upgrading the frame's existing armor, a shield was added. This proved to be more difficult for pilots to operate with, as to protect themselves properly they had to intercept incoming attacks with the shield instead of relying on the frame's armor plating. Most regular combat pilots loath these frames for that reason, but hand-hand experts enjoy the quick movements of the frame itself and the more refined control allowed without bulky armor.
A classic collection of clever connections. I like how smooth and neat this MOC looks from the front. The triangle sign works very well as the pelvis and I think that the shield is a good idea too.