Well using the method I normally use Christian, (its a very complicated mathematical formula you see) so, if the estimated weight of the fish is about 5lbs,...let me see, yes, here we are, I have the answer!
I would then add at least another 5lb on top (this is the formula that a lot of anglers use when sending in pictures to the angling press I believe!)....
CONGRATULATIONS ON YOUR 10LBBREAM CHRISTIAN!.....NOW IF YOU WANT A 10LB BARBEL...GET ONBACK OUT THERE ANDREMEMBER "WEIGH YOUR FISH THEDEANOS WAY"whatever it is+ 5lb and you will always go home happy...and the envy of your mates and dad!hope this helps!