IM/IM sounds really tight for a grouse gun. With respect to what SkeetTX Mike's conservative approach, I'd still open the first shot to an IC for that first year. That leaves plenty of choke for playing with later but puts some additional utility in the gun, and it leaves enough choke for the other Mike's approach to using it as a pheasant gun. IM/IC is not a bad 20ga setup for most situations.