Zippy pacing may be the single most important element to a successful stage production of Philip Barry’s society comedy “The Philadelphia Story,” which opened last weekend at Penobscot Theatre.

About the emotional escapades of an upper-class Philadelphia family in the 1930s on the occasion of a second marriage of their daughter, the famed Tracy Lord, “The Philadelphia Story” is loaded with witty, self-confident characters whose thoughts come out and zing around like bullets in a steel room. Ideas ricochet so quickly in this play that there’s simply no time for pause.

In a word, it all has to be very “yare” — the word Tracy uses to describe a boat that is fast and bright.

And the real joy of the play is that the characters make moral progress — with that triumphant Hollywood kind of shine. The basic plot outline, which many movie buffs will recall from watching the rollicking 1940 movie with Katharine Hepburn, Jimmy Stewart and Cary Grant, involves educating Tracy about the responsibility she must take for her own life and decisions. But along the way, there’s just enough dazzling champagne to bring out a little fisticuffs in everyone at the old country manor.

Thank goodness that the primary players in this smart cast, which was directed by Lisa Tromovitch, have the necessary pluck to make this play work. A good deal of that sparkle comes from Hilary Redmon, as Tracy. Redmon turns in one of the season’s most convincing performances with her poised energy and to-hell-with-you debutantism. She’s a slight woman who packs a punch, is serious but has a nutty side that can kick in at the tip of a glass, and she, more than anyone, brings an elegance to the household.

John Sarrouf, with his dashing moves and subtle sense of humor, blithely portrays her ex, C.K. Dexter Haven, the man she loves to hate — and hates to love. He breezes in like a swift sea craft, splashes who he has to, and then slides out again, leaving everyone a little sorry to see him go.

The other two players who make up the heart of this production are Ellen Hardy and Andy Brownstein, as slickly cynical magazine reporters clandestinely covering the society angle of the wedding. Hardy captures her character’s canny wryness, but she also shows a more compassionate side, and the balance is done with quite a lovely touch. Too bad costumer Ginger Phelps, who has dug up some gorgeous vintage clothing for this show, doesn’t allow Hardy to be more glamorous. There’s no reason why she shouldn’t be.

Brownstein, who in real life is a reporter for this newspaper, adds a blustery liveliness to the show. More than anyone in the cast, Brownstein conveys a sense of the 1930s — both in his manner and in his immensely entertaining comedic timing.

Shaun Dowd, as the harmlessly lecherous Uncle Willie, doesn’t miss a beat with his amusing commentary that runs through the play, and Eric Dean, as Tracy’s brother, has a flashy intelligence, too.

Young Stevie Dunham, who plays Tracy’s little sister, jauntily takes on the spirit of a precocious rich kid. She could even go further with it, and, certainly, no one would mind if she turned up the vocal volume.

Andrea Itkin and James Richardson gracefully play the all-accepting Lord parents, and Kevin DeBeck, as the fiance George, is just a nice fellow who inevitably drowns in the wake of this high-speed crowd.

Tromvitch keeps things hopping, an amazing feat considering that Jay Skriletz’s split indoor-outdoor set tightly packs the stage. Tipping her hat to political correctness, Tromovitch has also “cleaned up” the script by eliminating all but one of the smoking scenes and re-arranging the script here and there to downplay situations contemporary audiences might find intolerable. Because it messes with the poetry and insightfulness of Barry’s writing, some may find Tromovitch’s tampering intolerable in its own right. But most won’t even notice the changes.

This production is mighty fine entertainment. There are a few glitches with lost lines and misplaced timing, but the show has some real bright spots as a romantic comedy about the haves and the have-nots. No, the social structure does not fall apart in the name of true love, but it’s awfully good fun to watch it wobble a bit while folks find their hearts’ desires.

“The Philadelphia Story” will be performed 7 p.m. Thursday, 8 p.m. Friday, 5 and 8:30 p.m. Saturday and 2 p.m. Sunday through May 18 at Penobscot Theatre. For tickets, call 942-3333.