It's worth trying the lines you have to see if they match your stroke, but my go-to Skagit line on that rod is the 540 compact. For Scandi lines I like 460-480 grains and have also enjoyed fishing the Nextcast Steelhead Finder FI at 515 grains. Good luck. Great rod.
I own that rod and have fished it for many years. It is easiest for me to cast when I concentrate the power on the Stab and forward cast with primarily my bottom hand. When I initiate all the casting strokes with my lower , the rod performs the best. Jmtc
I use a 6/7 Winter Authority that performs well. I think it’s about 510-520 grns. I have the Nextcast floating tip for summer work and fish the Rio MOW’s for winter. Rob Allan’s recommendations are always spot on.
These are great rods and the fit and finish are superb