If you want to stuff them full, you can. Just be aware of a couple of things. One--it's going to be a continuous fight to get them closed! Two -- it's going to be heavy!! Try it out & you'll see what you are comfortable with!
If you have a zipper foot and/or can move the needle position to the left, it's not too bad when you sew one puff together. However, when you try to sew 2 puffs together -- that gets tougher! You may want to enlist a child/grandchild's help to stuff them! It's a fun, great project!