I built a 15 weight rod for my son to keep on his boat incase someone decides they want to give it a try. I think it has done in blue sharks around 100 lbs, yellow fin tuna to about 40, and quite a few mahi mahi. Striblue you arer on the right track about the reel, you could use a broomhandle with guides for a rod. From experince, :eyecrazy: get an anti- reverse reel and carry lots of backing.and always have a week-link in your leader system say 20 lbs.
its not very good seeing your flyline disappear. I also found if you are trolling a fly one wants something that is going to throw a roostertail in the wash, the bogger the better. I was experimenting with a Parrakeet Fly made of yarn, hard to tie, but works pretty well. If you are chumming be sure to have several chum flies.
At the winter shows talk to Captain Bill Brown of the "Billfish" out of Westerly He has been bluewater flyfishing for years. I will have to post some bluewater flies