Friend of my son needed help magnetizing a Predator. I've never built a Predator, may never have done one on my own, so this gave me a chance to give it a try. Not to mention, it was a great excuse to procrastinate instead of hitting the paint pots. Though much of what I did has been seen before, I thought I'd show how I did it. I already had magnets, mainly in sizes 1/16" x 1/16" and 1/8" x 1/8" cylinders, so I concentrated on using these. I actually came about having the 1/16" cylinder magnets by mistake, and often wondered what I was going to do with 500 of them. They've actually been quite useful.
I started with the side sponsons, as I figured most of the work would be involved there. First I drilled out the normal attachment holes on both sides with a 1/8" bit, and glued in the magnets here. I used the 1/16" magnets on the sponson arm, as the arm's width wasn't wide enough for a 1/8" magnet. To ensure a good hold, I doubled up the 1/16" magnets on the arm, both side by side and lengthwise to fit in the arm. You can see the before and after pictures above.
To the right is my method of attaching magnets. Once I glue the sponson arm magnet in place, I put a piece of wax paper over the magnet and let the weapon side magnet attach on, holding the wax paper in place. This way I can glue the next magnet and know it will line up perfectly. For gluing magnets, I often use a metal epoxy called JB Weld. 
It's magnetic so will surround the magnet as it cures giving a good hold. Wax paper is essential though, as you don't want it surrounding the magnet and bulking up any surfaces you want to keep flat.
Below are the finished pieces.
Next up is the turret set up. This is very straight forward, as the pins on the weapon barrels are exactly 1/8", so no drilling on the turret is required. You do want to add some green stuff or glue sprue pieces inside the turret to keep the magnets from being pushed too far in when you glue them in place. For the weapon barrels, simply remove the pins and drill 1/8" holes. Important here to line up the magnets in the proper direction. I actually did not use the wax paper trick on this one and regretted it. I had not inserted the magnet far enough into the turret hole and had to pry it out because there wasn't enough room for the barrel piece to fit in.
For the back of the turret, I used one magnet here. I've seen a lot of folks use two, and that's fine, but as long as you don't use too much paint between turret and box/power pack, one should to be strong enough. My magnets are N50s, which are almost the strongest magnets you can buy, so two may be better if weaker magnets are used.
You can see here and above how I've added magnets to hold the hatches in. Another fairly straightforward magnet application. On the closed hatch and in the turret hole, a piece or two of sprue is required to build it up so the magnets meet at the right spot. I used the SM gunner as the basis for placing the magnet. I wasn't quite happy with the location, as it wasn't quite center. They still rotate, but I made the mistake of using the SM gunner when I lined up the magnets in the hull hatches, so the other fill-in bits don't marry up quite right. You can see what I mean in the Predator top shot, I hope. The right hull hatch hole is centered, so fits everything well. The left hull hatch hole is set back a bit. While the hatches work fine, the other fill in circular bits sit funny, as their magnet is centered. Minor annoyance. The bottom of the turret is what you see here. Filling the hole here is a piece of sprue with a magnet it in. It attaches to either of the two magnets seen on the sprue bits crossing the main hatch. While the hatches themselves have magnets on them to hold them in place, the turret top bit does not. The strength of the turret magnet holds the two sided top bit in place so you can use it either way. If I had the bits to make a Razorback turret, either of the three vehicles could be made from this set up.
The side door and sponson parts are also magnetized. I couldn't figure out a standard way for a single set of magnets to hold both the door and the sponson, so I used different magnets for each. The sponson uses 1/8" magnets in a single location, while the doors use 1/16" in three places two at the top and one at the bottom (bottom not shown). I actually placed the bottom magnet after taking all these pictures because, as you can see in the rhino picture at the top of the page, the bottom of the door hung out. Once painted, the magnets will hardly be noticable.
The back hatch uses 1/16" magnets at the upper corner of the door. The 1/16" magnets are perfect for these doors. They are small enough to fit in the narrow plastic part, and strong enough to hold the lightweight doors in place, but not so strong that you have to struggle to open them. The only bad part is there is little room for error; you need to be careful where you drill.
