Well it took a bunch of spare hours this weekend, but in between doing the camo pattern for my Novamarines scouts I built the first rhino chassis for my Space Sharks. I used 1/4" rare earth magnets from Lee Valley. Nice thing about these was they painted a red dot to show polarity - made using them a snap.
Following mostly this tutorial;
I have it magnetized so it can be a Rhino, Razorback, Predator, Whirlwind or Vindicator.
I also have both front hatches, the front (vindicator demolisher cannon/siege shield?), the underside (for dozer blade/siege shield?), both sponsons (for predators), the top (predator, razorback, whirlwind), as well as four parts on the tracks (for upgrades) magnetized. I count 11 magnets per chassis (Front, Underside, Hatchx2, Turret, Sponsonx2, Bodyx4) plus another 1 per demolisher cannon, sponson, or predator turret) making a total of 15 per vehicle.
I have no pics yet but don't worry this won't be painted anytime soon, so you'll get a nice series of photos to show you how I managed it all. No drilling required.
I also built 3 twin lascannon razorback turrets out of spare Land Raider sponsons.