I like the look of Transfer Lebensohl. In general though, overcalling is easy with shape, and responding to partners t/o is also relatively easy with shape. You can always choose whether to overcall with a less than ideal shape, so that is a matter of partnership style. More problematic, and unavoidable, what does advancer do when weak to low intermediate with a balanced hand and is wishing partner hadn't overcalled ? (2S)-X-(P)-? (2S)-P-(P)-X-(P)-? Do you have any special sequences initiating some kind of up the line scramble (depends on how pure your t/o is) Are there any modern treatments that include a penalty element, like the original Hackett idea ? (I don't mean when a t/o, often in 4th seat, is converted to penalty)