Modified choke with 7 1/2 shots is good.
The more important thing is to practice skeet shooting with a gun that will come up naturally at the right shooting position.
You can shoot the same target shells using the same shots, that way your velocity is the same for instinctive shooting. Target shells have enough inertia for Grouse.
I shoot a single shot 20 gauge and it is a sweet gun for upland.
I don't find it fun shooting them on the ground or sitting on a tree.
Good luck on this.