What infusion set do you use? And do you use different ones for different areas of the body? It looks like there are 3 types: inset 6mm and 9mm and inset 30 13mm. We use the inset 30 on the bum area, but need to move to a new body area. My son is lean so would the 6mm inset be better for the tummy and arm? We tried the arm with the inset 30 and it hurt too much.