On a theoretical scale, I would say that the precentage of a green that is pinnable would be related to the size of the green. If the green is in the range of 2500 sqft, then it had better have in the range of 90% of the surface pinable of it will likely not survive on a course that gets any number of rounds. But on huge greens, you can go to 10% pinable space and be ok. I am trying to think, Kalen can help here, but I would say the 7th green at Thanksgiving Point is probably in the range of 25,000 sqft (I might be wrong there, but its really massive, probably near 75 yards deep and 30 yards wide, maybe larger) So, on a green that big, 10% would give you 2,500 sqft pinable space. Of course those size greens are outliers. But in theory, the minimum percentage of green space that needs to be pinnable depends on the overall size of the green.