The official line from Dexcom Tech Support is that the ONLY place an adult can attach their sensor is “above the waist”, so if asked where the sensor was attached, I am uncertain of what their official policy is about what would consider voiding your warrantee, but, I would be careful.
I’m thinking that any action that takes you beyond their recommendations is likely to cause somebody trouble if it is revealed or disclosed to them, “so think before you speak”. I find that when I get too involved in trouble shooting issues, I need to step back and script my side of a telephone conversation before I get too involved with the tech support staff on the phone or during an on-site chat.
It seems that no matter how helpful these folks may seem, they still work for the company that provide these product to (or for) us.
Arnold