Magnetized backpacks for Chaos Chosen

Introduction

I bought a box of 5 Chaos Chosen (with full command) specifically to use them in DnD. However, they do look close enough to mutated Chaos Space Marines (full plate, face-enclosing helms, horns, heavy weapons, etc). All they miss are the iconic generator backpacks. I want to magnetize them, so that I can then reuse them in Warhammer 40k.
Note that they are already painted. I stuck the magnets in their backs before painting, but I only got around to creating the backpacks now.

Assembly

Not much to assemble on the metal kits, but here goes. Note that I actually glued on the heads and weapons after I inserted the magnets. Otherwise, I might have exerted too much pressure on certain points, and they might have fallen off.

Inserting magnets into the back

I was extra careful when drilling the holes, but I still couldn't avoid damaging some of the iconography (chaos stars and arrows) on the armor. Some did present a nice clean surface, so that was easier.

Finally, insert some green stuff to avoid space around the magnets, then the magnets themselves. Use a toothpick (or anything non metallic) to scrape off the excess green stuff.

Note that I did not magnetize the squad champion. He wears a chain cape which I considered impossible to work with.

Creating the backpacks

I received some backpacks, but the side parts were cut off, for some reason. No matter! We have skulls.

First of all, I needed to fix magnets to the backpack. Since they aren't space marine "bodies" with a flat back and suitably placed pauldrons, I had to adapt a bit. Place a magnet on the back. Stick green stuff on it. Push the backpack in place. Let it harden for 24 hours. It worked, although it looked... unstable.
(Picture is taken at a later time, after additional work done below.)

Now for the backpack sides. I created some stubby cylinders, and used them to "assemble" the backpack.

After letting the green stuff to settle and harden for a bit, I used my sculpting tools to work around the cylinders, making them thinner and more uniform. They are supposed to be metal connectors, not hoses or organic parts.

Finally, I reinforced the magnets by wrapping the excess green stuff I had mixed around them.

Finished!