I like to run the main line to a good bead-chain and then connect that to the front of the flasher with a sturdy clip akin to the DuoLock as pictured above.
I cut anything off the bottom of the flasher except the ring.
Then I put a clip that is similar to the Duolock there.
When I tie a hoochy or spoon I put a barrel swivel on the leader at front.
I lay it all out and measure from the back edge of the flasher to the nose of the hoochy for leader length.
If I want a 36" leader, by the time I factor in the clips and barrel swivel on the leader and flasher, the actual leader length may be closer to 34".
I pre-tie all my hoochies and spoons etc. this way....then all I have to do is clip them on and they are free to rotate (avoiding line twist) at will behind the flasher.
For me the leader is always measured from the back edge of the flasher to the nose of the lure and that includes all clips and hardware between.
GENERALLY speaking:- Sockeye:- 24 to 27" leader ( trolled a bit slower than for Chinook most times), Chinooks:- 34 to 42" ( I get most success at 35 to 38"....about 2 to 2.3 mph). Coho:- same as Chinooks but go faster. Winter Chinook:- sometimes up to 45"
Many factors affect leader length:- boat speed,current direction, "drop-back"(distance from down rigger line to flasher.....I like to go at least 15 feet back), and brand of flasher.
Spoons for sockeye:- any where from 27" to 42" behind flasher.
Chinook spoons:- 52" to 72" leader (30lb test)behind flasher.
Bait/Teaser behind flasher:- anywhere from 5 feet to 9 feet, depending on area and time of year.
These are just general indications:- "Fishing Rules" are broken everyday, everywhere.
I like to use 30lb. for Chinook spoons, 25lb. for sockeye spoons and hoochies, 40lb. test for Chinook hoochies, 50 and 60lb. test for flies like Ace-Hi and Flash-fly etc.

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