I have asked this question to at least 3 well known bowyers whose names you would recognize who don't publish a minimum gpp, and they have all responded with a number under 8 gpp. The usual response has been around 7 gpp. Some years ago, I was into shooting low weight arrows to improve my 3D scores, but I eventually came to realize that the bow was much more pleasant to shoot if the arrows were at least 8.5 gpp or higher, and that at my level, it would be hard to tell the effect on my scores anyway.
I'm not stating the names, because they may have reasons of their own for not publishing a minimum gpp, and if you're interested, you can ask before you buy a bow.