Ok Tom, I'll bite, as I participated in the event twice and I also had concerns before I participated the first time.
The location and organizers has *everything* to do with how many is too many.
In the case of the Nephi events, there were multiple factors which made the high number of participants a non issue:
1- PowerFlarm mandatory. This mad a HUGE difference. I just can't say enough on how much it reduces the risk of mid air.
2 - line holds. The organizers held the line whenever there was even a minor congestion over the field.
3 - no start gate, which means everyone left once they topped out in the first thermal.
4 - multiple ranges and directions to go, so everyone spread quickly.
5- multiple options to land in case of congestion in the pattern: main runway, the grass parallel to the runway, a cross runway.
6 - since it wasn't a contest, most pilots only flew some of the days, making the max number of gliders flying on any given day at no more than 50.

So to answer your question, for Nephi OLC camp, 60 gliders are just about right.

Ramy