Yes, the magnets as shown are too far apart. At the risk of having my head detached from my torso, I suggest he figure on a coil diameter twice that of the magnet with the coil center the same diameter as the magnet, which seems to be a pretty standard design. Find out what magnets are available and which size allows the proper number of coils to just fit nicely around the rotor. For instance, if he was doing a 18/24 design, those 18 coils need to fit nicely around the rotor with each one touching its neighbor. Note that I didn't say anything about him trying my design.