Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Pin them. I chop the tab off my metal minis and pin with large paperclip thickness rod (resin bases). I usually pin both feet. If they're particularly large chunks of metal, I'll throw a little greenstuff in the hole, pin through it, and put a small blob on their feet as well.
This is Guardsmen/Necromunda models, so slightly bigger feet than Sisters probably

None of mine have come off the base yet from normal topples and jostles, and I think they only way they would is if I dropped them off the table or something drastic. Even then I'd be more worried about the rest of the model coming apart rather than the base.