I too have a Symetre 4000 with a 9'6 rod. Can cast a mile with my set up. 40 lb power pro with 20 lb seaguar blue label flouro leader. Have never lost a fish and have never lost any gear after consistently casting spoons, etc.
With heavier flies i tend to add a haul when im roll casting. It helps get that line speed up and that heavy fly out of the water. Check out some single hand spey casts on youtube and practice, practice, practice!
Braid starts taking in water after repeated casts. Just stick to mono. I use suffix seige personally. In addition, mono acts like a secondary shock absorber when fighting a larger fish meaning less break offs.