QdanT:When i made the lid i cut the shape so there was about 7-8mm more than i wanted,i aimed for about about 5mm to form the lip of the lid so the extra that distorted and wrinkled could be cut off.The outside curve was easiest to form,the problems started when i was following the curve on the handles side.You shape it in one place and it distorts in another!!Thats when i applied the heat.You know when its work hardening because it becomes very un-weilding.I was heating the lid edge to an orange-approaching yellow colour,this allowed me to form the shape and hammer out the creases that were forming.The whole thing was clamped in a vice do do all this.
Im glad i read lots about tinsmithing and sheet metalwork!I hope this ramble has somehow answered your question.