well as far as the predetor you will need 2 whole extra spnsons and magnatize them and you can cut the ends of of the twin linked las /auto cannon and put a magnet there
i dont see why you would need to magnetize a dread you can just get more arms and switch them out
im not sure about the emperors champ i dont own that model but i just magnetized the new commander set and i love my options i can change him between battles with all the gun and CCW options in the box |