i agree with alan its very easy to make a winning tactic for a side like barca they have the best players in each position even if some of them are big time overated *cough*ronaldinho*cough*
ive been barca before never even changed anythin in tactics just went with the standered it gives u when u take over did no changes at all and yet still won the league quite easily
now im not saying its a bad tactic just is useless when its been made with only one of the big teams and not tested with any 1 else
i allways make my tactics with lower league teams since i tend to play down in the lower leagues alot more then top leagues and then if i do get to top leagues or fancy a change i just tweak one of the tactics i made for my lower sides | 
