My dad is heavy into building motors. We like to use truett and osbourne wheels when original wheels are worn out or un usable for some other reason. They usually need a few balance holes, my dad turns them on the lathe to get some of the weight out of them and reduce balance holes.
With that little bit of material taken out of the fly wheel , you need minimal balance holes. Check it out both of these wheels balanced with only one hole. My dad has things figured out.