Re: poor handling at top speed
After you have the correct weight, (wraps of solder), added to the spoke, put a dab of silicone adhesive on it to keep it from moving. It doesn't take much and if you crimp the lead to the spoke you might not need anything to keep it from moving. Additionally the centrifugal force as the wheel spins will keep it out where it will do the most good.
To add to this; I've done some experimenting since that old thread that Barley posted a link to was entered. I've found a significant difference in ride after balancing my cruiser wheels and, the 'Slime' most certainly effects the balance until after it has distributed evenly throughout the tire. Cold temperatures increase the effects. Like everything else, the warmer, the better.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"