scott - mike vegis answered that in a thread i posted way back when. he said if i remember that the ryder cup had 25,000 per day and that the usga was shooting for 30,000 per day as optimal. pinehurst had 40,000 by comparison.
here it is copied
"Here's a copy of a post I made a while back on the subject...:
We've spoken to some USGA people and they say that at Pinehurst, they had 40,000 people. At Oakmont, they had 24,000 people. They think that 30,000 is ideal. We had 25,000 at the Ryder Cup with limited grand stands. Put a few more out and we could handle the crowds. Cougar Island (owned by Kiawah Development Partners-the island's real estate company) is just across the entrance from The Ocean Course with hundreds of acres that could be prepared for 1) hospitality tents and 2) additional parking (with KDP cooperation). We also have the old Bagger Vance hole for hospitality tenting. During the Ryder Cup, we had off-island parking with buses bringing people in. Our new 255 room luxury hotel near Turtle Point will be completed in Feburary of 2004. The Charleston Metro area has over 16,500 lodging rooms in addition to ours. All in all, we think we have the logistics to hold such an event.
And, when we redo the clubhouse out there in a couple of years, we're looking into the possibility of having some small bungelows out there near the 1st tee where people can stay. I'm sure, if we ever have The Open, they'd be used for hospitality... "