You can stack coils and in my Stack Patent # 4,524,667 (June 25, 1985) I used two bobbin basically stacked or mounted horizontal on top of each other. I use a vertical North & South magnetic field either in bar or rod magnets. The two bobbins are hooked up electrically opposite each other for a humbucking effect. By having a single magnetic polarity facing the strings, the bobbin can be made to fit into a single coil slot or cavity and was basically introduced to fit into a Fender Stratocaster single coil cover. My first prototypes were given to Buzz Feiten during the early 80’s and had been seen and heard by others.