I just got back from the Bahamas & I used 90" furled leaders i made with
Berkley Vanish Flourocarbon 4#. The taper is 3-2-1-1-2-3. I caught some bones up to 3-4-5 #'s & it handled them well. we had quite a bit of wind & it handled it well. I picked up a Barracuda about 30"'s using a wire tippet trolling . I was using 10 or 12 # flouro tippet most of the time & on one occassion I went to 8# for spooky fish. I love these furled leaders & will never go back to straight mono.
The twisted leaders you're talking about. are they those Singapore Leaders ????. If so there is a lot of info on the net about them.