This quilt looks great!
As Tim mentioned, a drawcord at the top is used to keep things cozy. But you've closed the top so now you have some soul searching to do.
The drawcord needs to be sleeved. If you just run it through the top baffle space it will constantly draw out down. You have a least three choices.
1) Make a tube/sleeve, open the top seam, and sew the tube to the inside of the baffle. Oufff!
2)Make a tube, open just the ends of the top seam, snake the tube through, and hand sew the ends in place. Tricky.
3) Or take some fabric and sew it to over both sides of top seam, folding both edges in for a finished look, creating a sleeve in the process. Depending on your skill level, it maybe easier to sew first one side, then the other.
In all cases you want to hem the ends of the sleeve first, again for a finished look.
Another consideration is where you want the cordlock - in the center a la Nunatak, or on one end.
The last consideration is whether to use a "static" cord or small diameter shock cord. Shock cord can keep the closure snug no matter how you move around. Some don't like it for just that reason.
Like all finish work, it is very visible and will be a testament to your skills. You may want to be done, but take your time, think it through, and end with a look that matches the rest of this quality job.