To make a transom stern, instead of a doubleender, just cut a slot and let the planking fall out. Ad a thin wedge. This not only gives a nice transom but also widens the aft area of the boat and broaden the waterline aft. Artillery grenades and high velocity rifle bullets are shaped like that. Helm a little offset.
Sideboard hold down by rubberrope to velcro closing.
Eight years and on your own keel. Sometimes it s god to be a kid. And a Dad. Short arms can t reach as faf as needed when making a sharp port turn.