My little educational turbine has a stator of only 3.5 inches in diameter and 50 turns per coil.  I think the larger diameter spreads the magnets out to far for good flux through the coils.  Its not very powerful anyway because of the air core (single rotor).  To get the maximum from the unit the magnet should cover no less than 2 coil legs at any given time and its better if you can cover almost 3 coil legs.

    Below is a picture of how the legs are covered in my "3 single phase" windings...

You can see the magnet covers almost 3 slots, there are 2 coil legs per slot so each magnet fluxes 6 coil legs intermittently and there is always 4 coil legs under the magnets at any given time as it picks one up and drops one.  The little turbine doesn't do this because the magnets are small and rectangular in shape but it does cover more than one slot at any given time.

You could possibly place them in pairs to make up the difference such as 2 North as a pair and 2 south as a pair ( NN space SS space NN etc ).  Also if the coils are thick you may need to double the magnets to get the flux to reach through the coils.  Or simply build a small dual rotor unit, this will draw the flux through the coils.  A simple steel disc behind the coils will improve the output but if its stationary will create drag ( eddy currents ) and will require more wind but improves performance.  Small units you can get away with it.  Large units will convert it into a massive amount of heat.

    Keep up the good work!  Looks like your having fun!

   The educational turbine alternator is quite poor as far as efficiency, its only a single rotor air core.

   If you mean the Lenz turbine I've seen anywhere from 37 to 42% measured from the shaft through a mini dyno.  I've only built small ones to date ( 2ft tall x 2ft dia ).  I don't know how they'll scale up.  It's on my project list this year to build and test a larger unit.  I plan to start with something around 4 to 6 ft tall and around 4ft in dia.  If it works out good then I'll build a larger one.  

   I haven't added it to my site as yet but the wings have been changed.  Still the same "J" configuration but I've added a different shape to the front of the J similar to the eipper 168 airfoil leading edge.  This reduces the drag from a Cd of almost 1 down to .5 while maintaining the open wing design which has a Cd of 2.3 on the downwind side.

Lots of fun this summer!!!