I made mine a little different to all those. I used clay and molded it to the shape pf my head so it fit properly.
I was making a Sailor Venus tiara. What I did was..
-Made/Rolled out a long strip the width I needed but quite a bit longer than I needed
-Molded the strip to the basic shape I wanted it
-Now heres the strange-ish bit.
- I take the rolled out strip ( usually on something flat so it can't stretch or break or whatever) I lie on my back with a long mirror propped up on my legs and with my head on the bed I move the clay to my head and change it to the exact shape I want then I take a bandana or a headscarf and tie it around my head over the tiara and then I leave it over night.
-In the morning I carefully untie the scarf and carefully take the tiara off my head.
-After that I put the tiara on the window ledge to dry out in the sun
This way it moulds perfectly to the shape of your head and tends to fit and look at lot better . If you want pics of mine just drop me a pm