Don't use the type that have the strip riveted to the plastic, use the type that have the strip bonded in.Check your rotor arm, does the brass strip on top move at all? If so replace it. Check your dizzy cap for cracks as well, just because they are new doesn't mean they are serviceable.
Cheapie pattern dizzy caps aren't a good idea either - I had to use one a few years ago & had an intermittent misfire which appeared at higher revs & was worse in damp conditions. Cured by replacing it with a decent one.