WOW, Nice machine, usually when I read one of these posts I look for the pictures first, then I go back up and read the post. When I saw the first photo I thought, I've seen that somewhere, and low and behold at the bottom of your text there it is, your in Vermont. I live in the Northeast Kingdom, Sutton actually and I swear I've seen your machine somewhere. Where are you? Email me if you wish.

Just a few thoughts (not that I'm any expert) First like others have said, judging by the size I think a center shaft is a must and won't affect air flow that much.

On your rotor it looks like you have plenty of room for more magnets, if you could collect enough of the same size for 40 more (23, You said you had 17) you could place them just inside the exsisting ones (aligned on the angle spoke the same, but closer to the center) and make a bigger magnet then wind your coils twice the size(or the same number of turns with bigger wire) in an oval shape. You could even use the smaller magnets to taper this 'bigger' magnet down towards the center, and make your coils even bigger (in a wedge shape). I would recomend that each set of magnets be the same size though(for balance mostly)  In any case larger wire is needed and if the 'big magnets'(made up of sets of 40 progressivly smaller magnets) is longer you can use more turns of wire in each coil. Or you could use sets of 40 of the smaller magnets you have and put a second and or third 'phase' of magnets on the rotor and coils in the stator progesivly closer to the center, on each spoke. I hope that makes sense. That might keep you from haveing to use tree trunk size wire for your outputs, It would be like having 2 or 3 altinators in one(each producing 1/2 or 1/3 of a total output). The wiring and phase guys could give you more exact info on this than I can.

Just my two cents, and I love to see that up close and for real, again nice work, you have the potentail for a real powerhouse there.