I find that performance is a hard thing to gauge. Generally speaking, the more mass you have in the hitting zone, the further the ball will be hit. However, pick up and balance also come into play, so it's entirely dependent on the batsman's preference. No point in a guy who likes a 2.8 bat using a 3.2 bat, just because it 'performs' better. The batsman will perform better with a well made 2.8 bat, and it's the batsman's performance that scores the runs!
Personally, I quite like to have the wood well distributed, but I use more of a medium weight at 2.10-2.12. For someone using a 2.7, unless you have a really low density cleft, I would take some wood away from everywhere, but mostly from the toe and the splice area of the bat. You want the right pick up without sacrificing too much of the length and the power of the hitting area. All down to the preference of the player, which is why going custom made if there's no options that appeal to that player off the shelf is such a bonus, and admittedly, something I've found myself taking for granted since joining this forum...