No, the pros recommend 10%, as an absolute maximum. Well, the real pros don't OC at all - they'd rather have a better, more stable card in the first place.
But 10% is the limit. Personally, if it were me (I don't want to OC my card) I'd OC to 10%, drop it by 5-10MHz to be safe and see how it goes. Of course, I would OC my card, but I don't have additional cooling. Is it totally necessary for additional cooling? Or is it OK to OC a card with no extra cooling other than your heatsink and the fan on the GPU card?
UFO-OzZie, is that product something like, StripPro... or something like that with "strip" in it? I saw a link to that somewhere - seems really good, but the 56.55 drivers incorporate exactly what your describing, as long as you install CoolBits to change your reg key.