7/8oz. is a common 2 3/4" shot charge, and I'm not so sure the pattern would be tighter at twenty-five, than at sixteen yards.
There might be options, drop the shot weight to 3/4oz, trim wad or shot cup petals, get some "shorties", Aguila has a 5/8oz. 1 3/4in shell. Why not use the gun, and send it out after the season, or don't send it out and let it be what it is. It's not a duck gun, let it make patterns with lighter loads, unless you got it to fill the freezer. I'd caution against using steel in it, don't forget the bismuth or maybe ITX.
