On the line, is the RIO good stuff, what If I order a 3wt instead of a 4wt? I'll confess I'm mostly attracted to it due to the discount, maybe I'm getting played.
Rio is good stuff, and that's a good price. I wouldn't rule out Scientific Angler Frequency at just under $50. I've been using the SA Frequency Boost on rods with similar actions. The Boost is a 1/2 size heavy. The heavier lines will load with 5-10 feet less line out, enable short casts, less backcast room, and larger loops for heavier flies. I don't know what the effective line number is for that blank but I'm guessing it loads best between 130-140 grains, or 4 1/2- 5 wt lines. The rod doesn't know it's a 4wt, it just loads when it has enough line weight, i.e. 35' of 3 wt line, 30 4wt, 25' of 5wt, 20' of 6wt, etc.
I "over-line" for shorter cast and more wind, and "under-line" for when I need to cast long with tighter loops, lighter flies. The Grand will not overload the rod. The extension sounds pretty cool by the way. Looking forward to seeing pics and hearing how it fishes.