Most of their answer will be due to hype and the fact that palace are playing bigger sides than them each week. Ask any neutral about the atmosphere at Selhurst when they were getting 14000 fans.
True comparison would be when we play Man U or Chelsea at the Amex.
It's a terrible idea. Just watch/listen to palace games, it's awful. Their famous 'atmosphere' consists most of the time of a few spotty youths banging a drum.