Make sure an attorney reviews bylaws before implementation. A vote of the incorporators plus the entire congregation, if desired, will activate them. Not setting a precise number for board size. Jesus had a great idea when he settled on 12 apostles. That's the high end of an effective working group.
Some states limit the spread on a board.
In Illinois, for example, the spread is three, so a board could have no less than 12 and no more than 15. Be sure to include the indemnification clause as an extra layer of legal protection for board members as they make decisions for the church. Another mistake is not ad dressing conflict of interest. Operating in a manner inconsistent with the bylaws is a big problem for established churches. At least every two years.