I totally agree with the feelings part of this whole deal. I don't believe you can have a seriously "casual" relationship...wether it be sexuall or involve only sex without actual intercouse without having some feelings towards each other. Who knows maybe she is one of those rare women who can disingage her feelings but I would bet money down that 99% of women out there cannot do that. (I am a woman so I can say that..lol) All you can do is ask her what she thinks of your plan and go from there.
