I have made the same sort of thing but here is a little trick to make it more sensitive. Put 2 magnets on one side and only one magnet on the other side. When balancing, have the prop attached to the one magnet side. This puts less pressure from the balancing shaft to the magnet in contact therefore reducing the friction surface that much more. It also will hold the free end a bit straighter because there is more force pulling on it than just one magnet but there is not any more friction. I found that before I did this that the shaft would walk a little bit on the magnet, now I get now walk. I purchased my magnets from Ace hardware, the super strong earth magnets, for about $3.99. I would have used free ones if I had them available.</p>