I talked with a well known gca recently and in the conversation, he reiterated what the USGA and others have said for a while......If you put a pin in a location over 3%, it won't be a good cup location.....period. Yes, I suppose you could create one with some kind of counter slope or whatever, but most would wonder if it is worth it.
Jerry Lemons (ASGCA) did a good green speed and slope chart (both in degrees and % slope, so make sure you know which one you are looking at) which actually shows a range. I don't recall the exact numbers so you would have to look up the chart, but if green speed is 8, it might be closer to 4%, and at 13, it would be less than 3%.
In the south, dormant berumda greens can easily get to 14-15 in winter, even if only 10 in summer when the grass is growing, so the question might be in what season. In reality, a busy public course down here has to know and assume higher green speeds and design accordingly for winter play, albeit, you might not need all 6-18 pin locations at the minimum slope, because play isn't as heavy, but that is a lot of brain power used to justify a summer only cup location when most golfers don't like it anyway.