did you read the specification chart on the magnet? you resonably have to place all the windings within 1 MM from the surface of the magnet to get the strongest magnetic field therefore more power. when i say the windings i also mean that ALL of the wire cannot be taller than 1MM from the magnet face or you begin to lose effect. Did you do the "paperclip test?" almost willing to bet you have 1MM of platic in the outer part of the holder. you need an open face design . I am working on one now when i have it done i will post the rotor.
if you check out my version (https://www.thingiverse.com/thing:2374343) i have added an stl file called 68MMframeless, it fits inside of your windings it also moves the 4MM magnets within a MM or so of the coil casing, this should give you better results with your mini, it also uses a fan blade for the hub so it can circulate air in case you wanted to beat me to it and see if it cools the coild any., the center rod in the design is 10mm i didnt know what yours was.