It does stay in the bra well. Thats a plus.
That's one of the first things I tried with mine! If I put it in the middle, I end up having to fish it out from where it fell further down later, but it stays very well if you just tuck it into one of the cups.
I should preface this part. This is my first post here. I am not a heavy vapor or into the technical side, and I don't use anything higher than 3mg, if that. Most of my juices are 0. I started vaping because 1) if I get much nicotine in my system, it makes me nauseated, but 2) I can't be around people who are smoking/vaping unless I'm doing it as well. I picked up an iCare Mini and my husband got a Kangertech DripEZ, if that tells you anything about the level of seriousness involved.
I gave my black and gray AIO D19 to a friend last night, as I'd pretty much quit using it in favor of the Kangertech Cupti. That being said...I had liked the AIO enough that after it fell out of my bag on an airplane, never to be seen again, I bought another one, and I'm cheap. I probably would have kept using it if I hadn't been shown how to lock the Cupti to keep the settings from changing all the time. The Cupti is overcomplicated for my purposes, but I wanted something I could change the battery in instead of plugging in all the time, and I have problems holding round pens and having them roll off places (see: how I lost the first AIO). The Cupti is probably going to be relegated to being my car vape for long trips and when we're going to be out for long enough that I don't want to refill the Mini 3 times, but the Mini is probably going to be my everyday ones that goes all over the place with me. I almost always have a big purse or backpack, so I can take a bottle of juice and the PCC with me.
I'm getting more flavor from the Mini than I was from the AIO or the Cupti, and the Mini fits in my pocket (and bra!) much better than either did (although the Cupti would stay in place in the middle

). I'm getting more cloud from the Mini than the Cupti, using the same juice (Smokin' Crow Cowabunga, 3mg, at the moment). The Cupti likes to fire in my pocket. The Mini does not, but we have a minivan with a sun roof, and if we crack it and the windows, the draw is enough sometimes to start the Mini!
I bought it at a local vape shop, even though it cost about twice as much as it does online, because we like our shop and he takes good care of us (plus, if he quit doing $5 clearance juices, vaping would be much more expensive for us

). The coils run $2 in the shop.