Thanks for all the replies.
When I have used the slip I have always maintained at least 1.3 (more like 1.5 probably) Vso, (judging by control response / wind noise more than ASI), and not more than a 25-30 degree bank. I've been taught that those are "safe"parameters. (172's primarily, but also in gliders lately (1-26's and 2-33's so far).
I've done deliberate spins in a 172, that required somewhat "artificial" inputs (though they could very well be produced by the unwary), i.e. full back-elevator / full rudder all with no-flaps extended. Have also done a "skidding" turn/spin in a glider and the subsequent recovery.
I *haven't* done much practicing on slipping / excesive-bank/ low airspeed leading right up to the stall. I *will* do that the next time I go flying (Next summer ? .. -12 -> -20C here right now !)
Mike