No offense...honestly....but to say that the collector on that is poor would be an understatement. That's a splay design, with four cheater cuts to make the entry angle. The flow penalties of that design probably outweigh any gain it'd see over stock.
I'm not trying to be critical of your piece, I'm just giving you the facts, so please don't take me the wrong way. The collector is just plain bad though. The convergence angle is WAY too steep.