blue hat I used plastic canvas and that was a bit of a problem. It having jaggedy edges I needed to wrap it in paper to slide it in. Then it worked great. The pattern says to use stiff interfacing. I just didn't see how this would be any good. The interfacing just didn't seem stiff enough. I decided to just go with the stiff interfacing as the pattern suggested and finish the hat. The interfacing turned out GREAT! The brim is plenty stiff enough and was easy to pull into the brim. "Trust the pattern!" Very seldom have a found a pattern that steers me wrong. This is what I tell a friend of mine when we work together. I need to take my own advice.
I've used several different yarns. The blue Red Heart knitted a hat that fits perfectly. The Hobby Lobby "I Love This Yarn" knitted a hat that is slightly smaller and a bit tight. I used a Softee Pink yarn and it knitted a hat that is looser. All using the same tension as the pattern asked for.
These 2 hats have no brim. I did that on purpose to make a beanie with the beautiful wave pattern.
All hats are now finished and ready for a head.