Our finding. For long rods 12'-0" plus, we found no benefit in casting using a longer than a 10'-0" leader. These are for swinging or skating flies. Floating line. With guys that are much better spey casters than myself, they normally tested our leaders with 6'-8' of tippet. Normally 8-12lb maxima.
On sinking heads, we use a 36" dredger leader. We offer three tippet ends, ring, loop and swivel. I like the swivel because with spey, you can get very long drifts. With a long the drift, the more chance of having your fly affected by current and cause line twist in your tippet. The swivel helps with this.
We also offer reinforced spey leaders. These leaders have a breaking strength of 30 lbs plus.
One major benefit of thread / reinforced leaders is that you can adjust the amount of stick by applying floatant. We tell first time users to apply floatant to the upper third of a long leader. Then after some time is spent using the leader, the user can either treat more or less of the leader to accomplish their specific desired result. Yes, you could apply floatant to any leader, but the floatant will not adhere / stick to standard poly leaders so well.
If you have any more specific questions, feel free to email me at:
Belwow is from of our customers.. biggest fish I know of so far on one of our leaders.
The 35 lb (according to guide Pat on right) salmon was caught on the Grand Cascapedia in Quebec Canada using an 8 weight Loomis rod along with a 9' Reinforced Spey Leader from Cutthroat Leader Co. a 10 lb tippet and also a Green Bomber (dry fly). The salmon made some spectacular leaps and runs in some very fast water and the leader did not fail (what else can I say).