If the hull was built as a single part then what you are suggesting will work, but I would like to see some glass in such a deep gouge. If the hull was built as two parts and then glassed together, then I would grind the area out and reglass it with layers of 1708 (biaxial stitchmat) extending maybe 6-10" on each side and well past the obvious gap. Put a couple of layers of mat on last before finishing. Fair then epoxy coat before bottom paint.