I had an RC glider growing up that had lead shot or fishing weights glued into the nose to balance it. The lead was held in place with either modelers cement (rubber cement?) or hot glue. If you're dealing with a glazed surface, I would stay away from hot melt. I've had problems with it adhering to slick surfaces.
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Hope for the best and prepare for the worst.
The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane