I have that rod and it is a favorite.
suggests Skagit 375gr to 425gr so you should be fine.
I like the Rio
Skagit Flight 425gr with T-8 and T-11 tips up to 8ft-10ft.
The Scandi lines for my casting style are Rio
Steelhead Scandi 350gr and Airflo Scandi Compact 360gr.
If you are only getting 50ft-60ft, think about refining your casting technique. Slow down and do not use the upper hand to punch the rod.