I was playing a match with the XM8s add on composite, and all it seems to do is get me overpressured more easily. The armor also seems less thatn it should be on the sides of the turrets and hull visually comparing the 150mm plates on the front and sides dont add up.
Not only the XM8, yesterday, I took a 105mm HEAT-FS shell from a Patria CT-CV right into the side of my Challenger Mk.3, and it overpressured me. Before that, I got hit by a 120mm HEAT-FS shell from a Leo 2A4 directly on the front composite turret armor of my CV9040C, and it overpressured me as well.
And overall, the “overpressure” mechanic seems completely busted.