Good going cleaning those nice magnets. It is looking good. It looks like your photos are too big and above the 100K size limit per photo. It takes too long for dial up fellows to view.
HINT:
If you want, you can shrink those photos down under 100k using "PAINT" program on your computer if you use microsoft. Just go to: 'Programs'; Then 'Assessories'; Then "PAINT" ; then load up your photo there from file and goto 'Image'; then to 'Stretch/Skew' and simply shrink it 60-80 percent and re-save. Then re-upload it here.
But One thing looks to be concerning to me from the photo. I see you are not using a heavy duty trailer hub. That support shaft looks like it is only 3/4" bore which is too small I believe. That big diameter rotor and those big mags have An ENORMOUS amount of force with a 10' prop. You might want to consider using something much stronger like (at least) inch and a quarter (1.25" diam shaft) BORE pillow block bearings.
Now to the alternator. Just a word of caution you may already know. If those magnets are not epoxied down yet you better be MEGA careful with them or two of them could crush your fingers off in a micro second. BE CAREFUL!
I would epoxy the magnets on - out close to the outer edges as Flux says.
It would be smart to put a steel strap around the disc as DanB does to hold those heavy high center of gravity magnets on very well.
You must choose which Battery system voltage you want in order for those in the know to help. It makes a big difference for the coils.
Many here say that for a serious Re-house system, 48v system is best with the least losses. But A good 24v/48v power inverter costs a lot more than a common 12v inverter. Many here say it is more than worth it for a serious system.
Hopefully, others with more experience than me will help you approximate your 13ga coils. (BTW, thats a good deal on the mag wire. Looks like half price to me)
Guessing from your first test coil, it looks like you are in range for the 48v system, even though 1" thick coils are very thick coils.
So lets say with 16 mags you get 5 volts with your test coil at 120rpm.
Since you have 4 coils in series per phase, that is 5x4= 20vac per phase.
Then you multiply that times 1.73 (Star connection) which =34.6vac
Then you multiply 1.4 with that number due to the rectifiers - which = 48.44vDC
130-150rpm which is a good cut-in for a 10' mill I believe.
If you want a 24v system you may be able to make thinner coils (5/8")and less turns with the same 13ga wire. Looks like you would then need half the coil voltage or 2.5v with a test coil. Or you may have to wrap the coils 'Two in hand' as Flux said.
For a 12v system you will HAVE to do the 13ga 'two in hand coils' and less turns.
No matter what you do, always bring out all 6 wires out of the stator for more options if need be later.
-Looks like you too have the addiction. It is SMART to have some RE now.