What type of Clay target shooting are you speaking about? It makes a bit of difference.
For instance, in modern Trap shooting, Barrels tend to be "Long" at 30-34 inches. In modern Skeet shooting, barrels tend to be " short " at 24-26 inches. Sporting Clays courses have evolved, but in the early days, the shots were most fast and close, so the skeet shooters and their shorter guns, with the balance point closer to the hinge, did well. More recently, I see longer targets being thrown, and the barrel lengths of the top competitors are lengthening out towards the Trap barrels. But, good balance is still what you find, even in the " longer" barreled sporting clay guns.
I don't think the length of the barrel on any BP smoothbore is as important as the Balance is.
The nice thing about fowlers with their half octagon, half round barrels, is that they balance so much better than a full octagon barrel. Moving a 42" or longer barrel after clays is no problem with a fowler. The long sighting plane between the shooter's eye and the front bead is a help for hitting the targets. And, some believe that the shot loads fired from the longer barrels produces better patterns out of a cylinder bore gun.
Our Mr. Brooks makes some darn nice long barreled fowlers, and hunts with them. I don't know how much time he has to shoot clay targets, but I suspect he doesn't have much trouble hitting them, either. But the key to the quality of his guns, according to members who own them and write about them, is the fine balance he puts into them. When you swing one of his long barrels, it just doesn't FEEL like you are swinging a long barrel. :hatsoff: