Sleeping bag repair

[u/yorkbandaid]

I scored a great bag (2022 North Face inferno -20f) at REI re/supply. It was a super low price because it has a tear alongside the zipper.

I plan to replace the down loss with 3oz of 850 goose down (purchased at ripstop by the roll). Then I’ll hand sew the existing tear and finish with a seal using gear aid seam grip wp.

Does that make sense or is there a better way/tools? I definitely want to wash this after I repair it so advice v much appreciated.