I'm not a fiberglass expert. But a through and through cut needs to be repaired properly just like an impact that would have cracked the hull.
Directions are in the maintenance manual, to include scarfing to widen the repair area, laying in epoxy, cloth, etc. Sanding and refinishing.

A simple repair, not done properly, could crack and get longer as the fuselage flexes in turbulence and with temperature changes.

BillT