Hey guys! I picked up the new Tervigon/Tyrannofex kit on Sunday. After a brief messing about with some of the bits, I determined that I could build the kit in such a way that I could have a Tervigon and a Tyrannofex at my disposal (just not at the same time).
The first step is to drill out the front limbs to accept magnets. I used some N52 3/16" x 1/16" from K&J Magnetics, so I used a 3/16" bit. The backside of the limb socket is nice and flat so it was no problem getting the bit centered and started.
Don't drill the socket all the way through, leave a bit of a lip for the magnet to rest in.
All of my Tyranids arms are magnetized with the same polarity, so I can swap talons to either side of the model. Here I've marked which side needs to go to the inside in blue sharpie. The magnet is glued in place with super glue from the back side.
Repeat these steps for the other half of the torso.
The next step is to prepare the Tervigon egg sac.
I used some larger 5/8" x 3/16" magnets for this, I think I got them at Hobby Lobby. I tacked the magnets in place with more superglue and then reinforced them with green stuff once the glue was dry. Don't try to glue them in place at the same time, unless you have very thick superglue that you can keep from flowing between the magnets or the other side of the egg sac. I just marked the magnets polarity and did them separately. The location on the egg sac shown in the pictures was perfect for the magnet diameter I used, plus it lines up with the edge of the part.