How to achieve high legroom reputation

Again, pretty much what the title says - how do you achieve a nice green bar of reputation for the legroom component that is displayed at the bottom of each route?

Take the all economy layout for the A320 which is 189 seats, how many seats would I have to reduce to in order to achieve a good legroom rating? Or, perhaps an economy and business layout for the A320? Or for the 747, 777, A330 etc...

Some help and discussion on this would be much appreciated!