Halving your air gap has virtually doubled the flux in the gap. The snag is that your thin wire has a much lower current handling capacity and will have far more resistance.
You gain from a lower cut in but your overall power out will be way lower.
You have probably not gained from the increase of hole size, the gain has been form flux increase.
Not sure what your original problem is, I certainly don't see why you are doing this unless you want to change to 24v. The current rating is going to be way down on the #16 wire at 12v.
Without knowing how it performs now I can't help much, but just getting more volts is not going to solve anything except possibly for a slightly better performance at cut in.
You really don't have a lot of magnet to handle a 5ft 6" prop so choose a winding that cuts in about 300 rpm for a fairly normal tsr prop.
If your tests are at 230 rpm then your cut in is a bit low unless it is a slow prop but you are not far from the mark.
If you just want to change to 12v then just double the turns with #19 wire or go for a bit thinner stator with a smaller air gap ( 1/2" stator perhaps) with less than double the turns of #19.
Using #22 is going to get you up to a 48v stator for the same sort of power out.
Flux
