I have a couple of 8 weights. They are a bit lumbering. I fish mostly ponds and have caught White Amurs up to about 30 pounds on rod & reel. Never tangled with one on a fly yet.
I've got a 10 weight I use for pike. After using the 3/4 weight that I usually use, it feels like a broom stick hahaha. Grass Carp would be interesting, I imagine something with green marabou drifted in front of them might do the trick