Once I determine the amount of the small lead wheel weights, I put some of the heavy duty double sided tape on them. Then I lay them out on a piece of cardboard and paint them a color that closely matches the covering where they will be placed. Clean the area with alcohol and stick them on with moderate pressure and I have not had any leave unexpectedly so far. I do not like the permanent type weight like epoxy and lead shot as it is too hard to change/remove if I decide to use a different engine.
Fred