In early September, the Hardly Strictly Bluegrass Festival made the difficult decision to announce a ban on coolers and opaque backpacks, citing the same security concerns held by fellow San Francisco fests Outside Lands and Clusterfest. Concerns soon abounded about long waits to enter the festival grounds, now delimited by perimeter fencing. Some thought the new rules might sway longtime attendees from coming.

But when the festival arrived, so did the crowds. And as it turned out, the only new challenge to those onsite was the addition of the fencing.

Security personnel onsite did not turn away concert-goers who had arrived with those coolers and regular, prohibited bags, though they were subject to search. By most accounts, entry was a breeze.

"The security wasn't the bad part," said Farina Khamsidi of Oakland on Saturday. "It was just the number of people trying to get in."

"They checked the bag quickly, that wasn't the problem," said Khamsidi's friend, Matt Van Pelt of Novato. "Once we got in, [people] bottlenecked, and I don't remember that from past years. There were also fewer options for seating. Before we could go up and sit in the trees."

Attendance seemed to peak in the mid-afternoon on Saturday, ahead of headliner Robert Plant's performance. Masses arrived for performances by Iron & Wine and Calexico, and foot traffic was slow-moving.

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"It wasn't very crowded [Friday], but [it's] more so today," said Keefe Northland of Berkeley on Saturday. "It was a bit tricky to get around, but I guess there's a good reason for it."

Though frustrated, fest-goers like Northland were sympathetic to the festival's reasoning for heightened security measures.

"I thought it was a sad commentary, but I certainly understood their concerns," said Betsy Karasik, who added she'd been coming to this festival from her home inWashington D.C. for over a decade.  "This used to be one of the most mellow festivals but even security lines weren't long at all ... By having security it seems to have deterred some of the locals that want to camp out here for the weekend.

"That might be sad but honestly I think it's reasonable."

Despite the complications, thousands of guests embraced and clearly enjoyed the opportunity to hit the park over the warm weekend to hear live music, particularly on Friday and Sunday when grounds were less crowded. Music fans danced, picnicked and lounged in the rare 80-degree heat.

"Putting the security measures in place because someone decided this large crowd gathering could be a potential target — is it worth it? It's worth it, it's pragmatic," said guest Bob Agnew.

"I don't need to bring a big tiki bar and large bags of ice for an event like this. Just some beers and friends — that's all I need."

Amanda Bartlett contributed to this report.

Alyssa Pereira is an SFGate digital editor. Email: [email protected] | Twitter: @alyspereira