Re: Fly size and castability
I agree to step up your tippet weight. I use 6lb P-Line Flouro on most occasions. Also if you have a wide open space, try casting to the side (we call it the guide cast LOL). Not as much wind.
If you have all the vegetation, you might want to think about a WET CELL sinking line. Not for poppers so much but nymphs. The belly of the line will drop, but put the fly up in the weeds.
Maybe the big fish are holding a little deeper.