loads of guys fish with 5 & 6 wt spey rods on the Vedder. Strat is in the grain window but i would be sure to look around at other line makers, I like Airflo and Scientific lines over Rio. the flight lines are nice but take a peek at the Airflo compacts or SA extreme shooting heads and then pair it up with a decent running line (i prefer the SA .021 running line)
have you picked up a reel for it yet ?
I suggest taking the rod with you when you do so you can test the balance of the rod/reel with the reel empty. you dont want your rod tip heavy or you will be fighting the tip off the water all day long taking away from the enjoyment of swinging flies. I personally like mine a little butt heavy so when the line is under tension (swinging) the rod lays perfectly level with the water in my loosely cradled fingers
being a 6wt and 12.6" i would bet your going to want a reel in the 8-9oz range. I have a 9oz reel on my 12'7" spey and its perfect
I know no one who fishes a 5 or 6wt on the Vedder. A 6wt is appropriate for pinks, bull trout and summer run systems with
small fish (where 12'6" rod is going to be annoyingly long), little else locally. Winter steelhead, most summer runs, chum, springs, sockeye... all too powerful for a 6wt. Fishing spey rods are a poor choice of tools for coho, so cross those of the list as well.
A 13'-13'6" 8wt is a much better all-round rod for BC.