Sorry to hear about your pain, I placed my first ever sensor where they recommend on the back of the deltoid and it just hurt the whole time. Where does the above recommendation come from? I'm just curious, the libre site shows a lady applying the sensor directly to the bottom of her deltoid, though she appears to have a decent layer of padding in that location so she should be fine!
When I came back to using the sensors I use the location you suggest above (which I would call the bingo wing location, though I don't have any wings myself!) Even then it can be rather hit or miss whether I get it in the right place (and it then works - if it goes near the muscle it either fails immediately, like this morning, or has very poor calibration.)
I think I may well try the stomach (I know it's not an officially accredited position) as having just had a day 0 failure, I've not really had any time to allow the very small regions (into which I can get a working sensor) to heal. I have a bit more fat on my tummy, though the downside there is needing to keep away from that location when doing boluses. C'est la vie.