FANS OF THE increasingly popular reggae-rock band Slightly Stoopid are known as Ese Locos or Stoopidheads.

Some say those names fit a bit too well.

One person, who has worked security at Bill Graham Presents shows for years, referred to a Slightly Stoopid concert as a kind of “final exam.” What he meant is that it’s the toughest crowd to deal with and the hardest show to maintain some resemblance of order in the building.

Saturday night, the security force certainly had its hands full trying to keep things running smoothly at the SF Weekly Warfield in San Francisco. Security was dealing with underage drinking, which one employee said happens more often at these shows, as well as with preventing fights, kicking out unruly patrons and, really, trying to diffuse a powder keg.

The result was a show that had an overall vibe worse than any other reggae show in this critic’s memory.

Of course, we need to qualify the term “reggae” here. No one is going to confuse Slightly Stoopid’s sound with that of Burning Spear or Toots and the Maytals. It’s not in the same class, and, thankfully, it doesn’t pretend to be.

Slightly Stoopid follows in the iffy footprints of 311, a reggae-ized rock band that appeals to frat boys wearing Bob Marley shirts and trying to feel “ire” by drinking Red Stripe by the gallon.

And, as the Warfield gig proved, the Southern California band is pretty good at what it does. For this critic’s money, Slightly Stoopid is better than 311 but still a ways away from reaching the heights of its main musical mentor, the ska-drenched Sublime.

The band — which began in the early 1990s when two would-be musicians, Miles Doughty and Kyle McDonald, met in high school in the San Diego area — kicked off the show with a stoned-out waltz through the mellow reggae number “Bandelero.” From that tune, which can be found on 2005’s enjoyable “Closer to the Sun,” the four-piece bandshowed its versatility by charging through SoCal-style punk rock, Jack Johnson-esque mellow surf music and something somewhat resembling hip-hop.

Although a veteran act, having logged about 200 dates a year for the better part of a decade, Slightly Stoopid still comes across like an informal group of friends playing at a frat party. The musicians keep it loose, fun, interactive and, above all else, very juvenile.

They also can get raunchy, exemplified by the performance of one particularly obnoxious ode to the lower region of the female anatomy — the title of which is too lewd to print even by omitting letters and using dashes. To be fair, though, it’s nothing racier than what is found in much of hip-hop.

Guitarists-bassists-vocalists McDonald and Doughty, who kept changing instruments and taking turns at the mic throughout the night, sounded particularly strong during”Runnin’ With the Gun” and “Officer.” In general, the reggae material was stronger than the punk and metal.

After a suitable run through the descriptive “Mellow Mood,” which benefited from nice horn work from opener John Brown’s Body, the concert hit its high-water mark with a joyous take on the great tune “Somebody.” The song showed that this is definitely a band with potential.

Now it’s up to the band’s fans — the Stoopidheads — to show they have the potential not to live up their nickname.

By Jim Harrington, STAFF WRITER, InsideBayArea