Save you're money when it comes to porting in a shotgun. The felt recoil reduction in neglegable and the muzzle blast won't make you many friends in the field.Best to have a shotgun that fits ,that's the best recoil reducer there is, period.
The mega mag craze in shotguns (3 1/2's in 12 ga.) is one of the worst things I've seen perpetrated on the shooting public. I go to the local Gander Mt. store and see racks full of these 3 1/2's ,I guess after one season the shooters finally figure out the abuse isn't warranted.