I use a GPX on my 5 weight TFO TiCr and fish warm water exclusively. One of my favorite flies is a cone head cactus chenille bugger with maribou tail tied on a #6 streamer hook, it's somewhat bulky and definitely heavy and I don't have any problem casting it with the above outfit. The Head Start lines are good buy since they have the same AST coating as the Mastery lines, one of the guys I fish with uses them on almost every rod he fishes including his 8 weight salt water rod. If I ever wear my GPX out I'll probably replace it with a Head Start.