Thanks for the concern - the Schroth is actually DOT- approved.
The shoulder belts are connected to the rear passenger seatbelt points, and the lap belt attaches to the stock driver seatbelt points. They have this tech they call ASM for anti-submarining that is supposed to apply slightly unequal force on the shoulder belts, which cranks the lap-belt in a way that locks the pelvis in the seat.
Pretty cool harness, but I think I need the shoulder-belt pads. Got it from a guy in the club who had it in his SVT Contour (badged SVT Hybrid - 3.0L Escape block, ported+polished Taurus heads, SVT intake).