The main thing is that I've been going along, I've stuffed them tighter and only used chopped up felt scraps. It's hard to tell in the picture, but handling them, you can tell a big difference...so much so that I'm thinking of opening the blueberry muffins back up and putting more fill in them.
One thing I should warn you about the pattern below is that the top circle is just a little bit big. As you sew it onto the bottom, every few stitches, you'll need to take a couple slightly bigger stitches on the top than the cooresponding stitches on the sides. This will gather the top, ever so slightly and make the top poof out more...or if that sounds too intimidating, then cut the top circle, just a TINY bit inside the lines.
And don't forget to try the scrumptious strawberries?