Nope, not a magnet system for the chest pieces. I used screw posts through gromets in the vest and washers and nuts on the inside. I did use magnets along the top and back of the vest to hold the vest close to the collar armor & back plate when I put those two pieces on over my head.
I have the SHACKMAN set. Long time ago, I've made a window on the vest, with a separate pocket for the second circuit AND battery. The LED circuit part is hot glued to the chest armor via a custom box made of SINTRA, that I've designed to protect the circuit from water, dust, and to easily plug and unplug the ribbon cable. It fits snug and as close as possible to reduce profile. The box is assembled with SUPER GLUE.
Also as a note, I made a really small frame, black plastic, to cover around and between every 4 LEDs (20 total divided by 5 groups) from the SHACKMAN top lights, to reduce the light projection to other LEDs at either side and create the proper effect.
The magnets are no longer an attachment method for the chest armor, which I substituted long time ago with snaps. (thanks Bobafettish).