I also used magnets to make my Raider crew stick to the Raider. I'd like to remove them when the Raider is shot down (or empty), but they fall off after a slightest knock if just "put on" the Raider. So I added 1 magnet to 1 feet of each of the crew (except the gunman who holds his gun tight enough), and I drilled the Raider's sides to put magnets there. Here go the pics. The one with the green stuff is where my drill went awry.
My best work is the magnet below the grill for the captain. I decided not to drill the grill but to do magic instead. I got a larger magnet (3mm x 1.5mm) and I put it below the grill. I then used other magnets to pull
it to the grill from below, then I added a drop of super-glue and voila! - my captain stays in place with no visible magnet on the floor below. The force is enough to keep him (and other crew mates) on the floor even when you turn the Raider upside down or shake it. And the snap when you put a guy near his place makes one's soul cheer with joy
When deciding, where to put a magnet on a ship's side, place the crew member where it belongs, and try to press his foot (the one you're going to magnetize) to the surface - that's what the magnet will do once in place. You need to find a position where this kind of pressure will not make changes in the guy's pose (so he/she still holds the side of a ship with a hand or the hook, for instance). Once you're set - drill.
I've also magnetized Ravager's gunners but that's too boring to tell about.
Cheers, hope you like it.