Try a SA Extra Distance line in the weight of the rod, have cast that line
on the rod mentioned in a 5 wt, 8 wt, and 10 wt which great results.
Also the best line I have fished on a Sage 8 wt TCR.
You only want to overline a rod when you're fishing in close (to correctly
load the blank), underline a rod when you must keep a lot of line in the
air.
This line will throw 60 ft rollcasts on the 5 wt.