I did the exact same thing with the same REI down bag. Your sewing looks much neater. I've had mine into the 20's with no issues. There are a few spots where the down is a little thin, could just be needing a good washing.
You can see it in my avatar.
If God had meant for us to sleep on the ground,
He wouldn't have created trees....
“Everybody needs beauty as well as bread, places to play in and pray in where nature may heal and cheer and give strength to the body and soul.” - John Muir