I needed a knot that would be able to connect 80 lb braid main line to 250 lb mono..the knot i use for lighter leader doesn't work..250 lb line is not good for tying, especially to a main line that is a fraction of the diameter. i can tie a good palomar knot to the hook though and it won't come out but all the info i could find for tying bigger leader to main line was "use a barrel swivel" or "crimp it." i also came across a knot called the stren knot, which from what i read would work with leader 200 lbs or better..it is basically like the double uni knot, except the main line tag is used to tie an improved clinch knot instead of another uni..the uni knot is wrapped anywhere from 1-7 times depending on diameter of your leader, and the improved clinch knot part is wrapped 5-12 times again depending on line diameter of your main line. alot of you may disagree with me but i believe the improved clinch knot sucks..it was the first fishing knot i learned to tie when i was a kid, and i stopped using it soon after, it is easy to pull out no matter how well it is tied in my experience..the other day i lost a big fish using the stren knot..the main line slipped right through the leader, a result of the improved clinch knot slipping. so i decided to create a variation of this knot that held up on an even bigger fish that ended up breaking me off very high above the knot. here is the stren knot...
on the uni knot, i do 3 wraps eventhough 1 is supposedly enough with the leader i use..i had 2 wraps on the one that was pulled out on that big fish
and here is what i do different..instead of the improved clinch knot on my braided main line, i tie a san diego jam knot with about 10 wraps, then pull it down tight against the 3 wrap uni knot in my leader..here is the san diego jam knot..its basically an upside down clinch knot, but it is stronger

i don't know if anyone has ever done this knot before, but i call it "silver king special" or "tarpon leader knot"
try it out, let me know what you think