On 5 Dec, 20:05, wrote:
Hello,
I built a 6wt rod and it has a slower action. In fact it throws a 5wt
line much better, I learned this by trying a wf5. I wanted to buy a dt
line for it and was wondering if there were any that compliment slower
rods more?. I know that there are wf specifically designed for fast
rods but wasn't sure about double taper line.
Thanks,
Brian

The line weight a rod will handle is independent of the action.
"Action" is defined as being the point to which a rod bends when
casting the optimal weight. If the rod casts 30 ft of #6 weight line
optimally, then it is normally referred to as a #6 weight rod.

http://www.stcroixrods.com/content.asp?id=70

Weights above and below the optimal weight also affect the action.
Using a lighter weight makes the rod action faster.

Judging by what you wrote, and assuming you are a reasonable caster,
then it sounds as if you would be best served with a #4 DT line.

This also depends on how you fish, the average length of line you
cast, and the size/weight of the flies involved.

TL
MC