i have caught them on 8wts but it isnt the prefered weight. Most of your sea-runs are going to be around 10 or 12 inches. The size will change as the year wears on but you rarely will find fish over 18 or so. I use a 6wt Xi2. very fast action rod.
I am probably going to build myself a 5wt TCR for the salt at somepoint. Or if i find a good deal on a 5wt RPLXi i will buy that.
good luck