Yes a larger line would be make it a bit easier to throw the larger flies. The question is, will your 5 wt handle the larger line ok? If casting distances are shorter, than it may . . . but if you are casting longer distances and it's a slow rod, it may not do as well. So it depend on casting distance, rod action . . . Try it and find out. Go to a local shop and try one of their parking lot lines.

Another option is lean toward the smaller flies. This is an interesting fly. It's Jack Ellis's Fence Rider Bug. It's a small deer hair but that he says can be thrown on a 5 wt.

-wayne