We Only Run Flys Behind Our Spin Doctors And Most All Have Leaders To Tie Them To The Sd, Then Our Leader From The Diver To The Sd is 24 Inch For An 8inch Sd And 30 FOR a 10 inch Sd, And That Leader Is 30Lb Seaguar, The Lead Length We got From The LOU Tackle Forum, It Is A Must Read For Salmon Fishing.
we do it like this
8ft of 40lb mono leader
spin doctor flasher
about 24" of 50lb flouro to the fly (we have been using A-tom-ic flys with the two hooks in pre rigged, you just need to tie a big clip to the loose end of the leader)
We have always put the front clip in the front hole on the spin doctor and the fly on the back hole that the two fins are pointing too.
For spoons we have done well with 25lb flourocarbon leaders about 6 ft long. with a 30lb main line for about 100ft that keeps the waterfleas off, then a braid backer down to the spool.