You are correct in the order it’s placed. I’ve been doing this foe years and have had no problem with the cannula piercing through. The Tegaderm sticks really well to my skin (I place it is locations with zero to hair). For me, it stays put swimming, in hot tubs & showers. But everyone’s skin is different.
Here’s a post with a detailed step by step explanation of the process I’ve been using ((which includes putting an additional layer of Tegaderm over Pods & Dex sensors…I do a cut out with the top layer so I don’t cover the Pod/ sensor). I can’t think of the last time a pod or sensor didn’t stay on for the full duration (excluding ones accidentally ripped off).