Machamp from the Furious Fists expansion has the ability "Fighting Fury". This ability states that all of your fighting type Pokemon's attacks do 20 more damage. Can this ability stack so that if you have 2 Machamps it does 40 more damage or with 3 Machamps 60 more damage? Picture of card at http://bulbapedia.bulbagarden.net/wiki/Machamp_(Furious_Fists_46)