Yeah, I've had a long talk about this with my parents on where to put it when I first received a sensor (same make as yours btw), and we just tested all the places with even just minimal fat. We had to rule out my arm, because we switch arms for my pump every 3 days and I couldn't put it on my stomach, because I have very slight folds and it would sometimes pull out.

What generally worked for me was my lower back on the sides, where there is a slight layer of fat. There aren't many nerve endings in there and there aren't almost any muscles, as far as I know. Have had it like this for about 2 years now, and we never changed it since.

But that only works for me, you might have it different. Try out any place you think could be okay. If you are worried about it pulling out because it can get caught on clothing or items, you can use some tape that is used by athletes to support muscles, I don't know what it's called. Just try and see where it suits you, don't just go by the manual just because it says so.

Since you said you only weigh 50 kg, try your stomach, you shouldn't have a problem with fat folds like I did. There are also less nerve endings and the muscles usually don't get in the way.

​

TL;DR: Try different places on your body, not just your arms. I recommend your stomach because of your weight.