I guess this may be a silly question, but I wanted to make some lotion bars and have a nice way to present them. If I buy a round metal tin that says it has a 3" diameter and I use a mold that has a 3" diameter, will my bar fit into the tin? I mean, do the lotion bars shrink - even a little bit? Theoretically, the bar would be the same size as the container and therefore, it would not fit into the opening. Any thoughts on this?