How to keep hubcaps on?

Hello, still have the stock 13-inch wheels on my 63 valiant, and my hubcaps keep flying off around turns!

Can anyone help me figure out how to keep them on? I suppose there is some physics to it somewhere, but I'm not sure what part is most critical. I've tried re-bending the metal to make it all look perfect, but they still fly off. Not immediately, but within a day or so.

I was told I could run screws through them into the wheels, but don't really want to do that, yet.

cheers, Ann

Hubcaps or Wheel covers?
I never had a problem with the dog dish style hubcaps,
but did loose a wheel cover a couple times.

Hubcaps on the light blue 1965,
wheel covers on the dark gray '64.