If you follow the plans you will get dreadful results if any at all.
You could probably adapt the alternator design to use microwave magnets but it would be large and heavy and would need lots more wire.
Just replacing the neos with microwave magnets would give you an alternator with a much higher cut in speed. It may produce something if you use the 48v stator on 12v but the thing will never be able to handle the intended power rating and the furling will not protect it so it would only work in a low wind area.
Flux