If Hal and Sinestro switched bodies, you can bet it wouldn't stop 'em from trying to beat the tar out of each other. Of course, watching them fight under those circumstances would probably be pretty darned funny, because you can ALSO bet that they'd be trying REALLY HARD not to damage each other TOO much: "My face! I just can't bash in my pretty, pretty face!"
Actually, this is all just an excuse to post the following. Just looky what I found! First, here's an Ivan Reis panel from Green Lantern #37 (2008):
NOW, check out this panel by Alex Ross and Doug Braithwaite, from Justice #11 (2007):
Coincidence? Hmmmmmm! Just different enough, yet similar enough, to make one wonder.