The balance of forces is very precarious. The dexterity is very inportant, and also very important to have time and patience. I spent two days to find the right balance of all the elements. Shape and weight of the spinner, alignment of the magnet base perfectly level, align the axes of the two ring magnets. For me it was the most challenging experiment done so far.
the top is made with a pencil, cut into 3.3 cm. on the tip of the pencil I glued a piece of aluminum foil. To fit the ring I used thick rubber made from an inner tube of a bicycle, but thickness can also doing many turns of electrical tape. To add weight, I attached magnetically 3 washers iron magnetic ring.
Pay attention to detail, this experiment is not easy. A tape around more or less change the weight of very little but can make the difference.
More info about this experiment here