I'd say 10oz on a barbel of this length and bulk (size) up or down in a few days is well within the norm? If the fish has stopped growing and is just 'fluctuating' on the annual four season cycle, impacted by the weather, available food and spawning, then weights of big 17 to 22 + would feel about the right range? If it's still growing! And over the next couple of seasons it gets caught towards the top of its then weight range on the cycle, 'Someones going to need a bigger landing net!!! I'm padding up for a few 'fast balls'!