All you gotta do is make a basic attachment, save its base (say, if a platebody is made, mostly from one geoset) as a geoset, import it on the model, then copy n paste the position values of the attachment point into the translation menu in Magos, and edit accordingly, record every translation edit you do, and add them all up. Use those three numbers to translate the attachment as a whole so that it'll fit perfectly once attached.
Oh, by the way, that's just a 'cine RPG' hero, with his own basic armor. The RPG characters themselves will NOT have leg guards and armguards, or a collar, aswell as shoulderpads and any sort of decoration. Those'll be all yours to handle.