To start with, 7/8's oz loads while not that uncommon for the 12 gauge are hardly the norm so to expecting them to work in a gas gun that is designed for 1 1/8 oz loads is a bit unreasonable in my opinion. I'm not saying don't open up the ports, just that the op should be aware that he's subjecting the gun to more strain than it was designed for if he decides to use higher power loads which are more normal and easier to find after opening up the ports, that's all. The A303 is a robust gun but it does have an alloy receiver so that should be respected in regards to load power levels. Lets face it, shotgun ammo isn't exactly overabundant these days so to expect to find loads that are not the norm is a bit unrealistic. There's circumstances where I will advise someone to modify a gun but many more where I will advise them not to.