We use them underneath the armor on our Plate Carriers, I'd say yes to avoid internal organ damage or broken ribs. Buddy of mine is a 240B gunner, took an AK round in the front plate from about 50m, still left a helluva bruise and knocked the wind out of him.
Sgt. of Marines, 5th Award Expert Rifle, 237/250
1st Award Expert Pistol, 382/400
D Co, 4th CEB, Engineers UP!! OEF 21JUN-20SEP2011