[Tigerlily.]

You can ask in the moment, but I still think it would be best to talk about it before hand, then it gives her time to really think it over instead of just haphazardly answering and then being sort of shocked if it didn't register, I know that, for me at least, in the moment sometimes I won't really think about what the other person is saying, and that would be quite a shock if she didn't really process it. If she says no, then she says no, in that case, you really shouldn't do it, but maybe you could explain that you are just curious. But if she says and it's not in the heat of the moment, then you know that she really wouldn't mind and you won't get kicked in the face or a more sensitive area due to shock during sex.