Tin casts better when it is thin and delicate, than when it is thick, because when it is thick it contracts in high heat. So if you want to mold a thick piece in tin, mold it only one one side, and if it is possible, make it hollow on the other side. In this way your piece will be neater. And then you can solder two half pieces together. But if you have no choice but to mold it thick, make the shape of it and mold force abreuvouers around the figure in this way.