poor kite!
The seam along the keel are a week spot (with or without mylar reinforcment) on modern kites, high wind flying and lawn dart are there to prove it.
Carl did a repair on one of the team kites recently which got a tear about 12" long near the spine. He appliqued a new panel over the top and cut the old one away apart from the last cm or so.
Might be worth replacing both red centre panels with a single one. Depends on whether you remove the nose / tail / trailing edge reinforcement, or keep a bit of the old sail in those places and applique as close as you can to them.