First, stick on ww's that weigh 250 grams each. They have the same hardness as regular ww's. Got loads of these, they're even unused. Glue was just not strong enough because of the weight of those things.
"Regular" stick on ww's, just that they now make them of pure tin. Melted down a batch today, I sure hope I come across a lot more of those.
Life is good.