In my opinion, porting a shotgun definitly is not worth it. It might reduce muzzle jump but that is about it. It seems to me that porting is most effective for high pressure firearms, and a shotgun isn't high pressure enough for it to make a difference. A really good article on porting shotguns can be found at
http://www.shotgunreport.com/TechTec...ChokePort.html
Gordon