I went ahead and added the elastic, and it made a huge difference. I used Dritz Thin Beading Cord Elastic which I found at my local Joann store for all of $1.59. I ran four strands of it through the knit stitches on the inside of the hat’s ribbing at the brim, one each at the first, third, fifth, and seventh round of stitches. It took all of five minutes and it has totally improved the hat beyond all reason. It is now just the right kind of snug…not tight enough to leave marks on my forehead, but not loose enough to slip off my (unreasonably straight and slippery) hair.
If you’re considering doing something similar to one of your hats, I have a few small suggestions. First, cut the elastic several inches longer than your actual head circumference. In this case, the cord came in three yard lengths, so I cut it into four pieces of twenty seven inches each. Run the elastic through the ribbing. Line up all the ends on one side and tie them in a loose overhand knot, leaving a bit of a tail. Tug and stretch the hat till you think the elastic is the length you’re going to want, tie the other ends in another loose overhand knot, and do not cut off the extra length. Wear the hat for a while. There’s a good chance you’ll decide the first length wasn’t quite right and you’ll want to adjust things a bit. I ended up loosening mine twice before I found the perfect size, and I was glad of the extra length.
If you look closely you can also see one of my dirty little knitting secrets. When I knit in the round, all my purls are twisted. Please do not explain to me why this is wrong and bad and terrible and how it is likely to cause the world to end. I understand why it happens. I know how to do them so they don’t come out twisted if I want to. I just like them this way. I find it easier and faster to do, and I knit so loosely that the extra bit of snugging up that the twists provides is helpful.