I run an POD store. All my products come from both Printify and Printful. As I was managing the shipping, I cannot combine both Printify and Printful into one shipping rate. For instance, I have 3.99 shipping. If someone was to purchase an item that was made from Printify and one from Printful then the shipping from the customer would be 7.98. I do not want this to happen, I want it to stay at 3.99. Does anyone know how to make this happen, if it is making any sense?