Eric,
Looked at the link you provided. Thanks. Berkley Trilene Fluoro : 4 LB test - Diameter = .007 = 4X. Not good. (for me), RIO 4X mono = 6.4 LBS, Seaguar 4X Fluoro = 7.0 LBS. Much better choices. (for me). Incorporating this Trilene 4X material into a 5 or 6X leader with a greater breaking strength would cause your leader to break back at the 4X section. As you know, when building leaders, ideally, you like the leader to be able to turn over the fly, so the first thing I look at is the diameter of the material and the stiffness. Then I consider the breaking strength of the weakest link. All things being relatively even, you would expect your leader to break at the fly, not half way up the leader. Basically, what I am getting at is that this Berkley stuff is too weak per its diameter. If I've missed something here, please let me know. I may be assuming too much! Won't be the first/last time I'm sure! LOL!!!!
Best regards, Dave S.