Magnets are great, but you have to use the really strong eart magnets.Some of those damn things take a good pull to get them apart.
I usually just stick with velcro, and they even have new velcro now that irons on for the fabric side.No more sewing.
Do we know for sure how the original chest armor was mounted? I know you can see velcro under the collar peice but is there a possibility they used something stronger on the chest? I can't find examples right now but I seem to remember seeing what looked like metal hooks of some sort near the shoulder bells. Maybe something similar was used on the chest?