An acquaintance has an Interceptor vest with the usual soft armor inserts.  He wants to add hard armor  plates, front and rear, and wants to know what types of plates to add.  He wants to use the original soft armor as backers for ICW plates.  He's not concerned with Lvl 4 coverage.  The less weight the better, within reason.  He doesn't want steel plates out of concern for weight, and is leaning toward shooter's cut, triple curve plates.  Carrier size is Large, so presumably so would be the plates.

What sort of plates would be optimal, and where should he get them?

Some suggestions for vendors, please.