I'll be going mid-september this year and have thought about bringing a lightweight shotgun with for grouse since they will be in season. The Rossi Tuffy .410 looks interesting and only weighs ~3lbs. Anyone have experience with this gun or .410 for grouse in general?

I have no experience with the Rossi Tuffy or 410s. I think if your intention is to ground swat grouse you might be fine. I personally would use a 20 gauge. It would greatly increase your odds of shooting a grouse on the wing.

Do you/ have you hunted grouse before?

My friend hunts turkey with a 410 and gets one every year. Yes, a lot of birds in flight I would go up.

I typically use larger, but do exactly as you're thinking and I bring a 410 on fall trips. I bring a small savage over under 22/410 combo. It works just fine. I find that up there wandering through the woods, I come up on them alot closer than when i'm hunting logging road birds with the atv.