Another good way is using a bolt( I've seen some nice plastic ones, like FP uses) glued to the armor, and have corresponding holes with eyelets in the vest. Bobamaker had a good tutorial somewhere out there. Just have to play around with how to temporarily attach the armor to get good locations for the hardware. Seem to remember that he used bent cardboard to act as the armor to get a template.
Getting the holes to fall where they needs to be accomplished first. Then locate the mock armor where you are satisfied with it. Mark the holes on the cardboard armor, then transfer the marks to the armor for placement of the bolts. Epoxy and allow to cure, then bolt up with acorn nuts.
Something like that....