Hi, I will try to base this on your original statement.
Spectra to mono, or Fluorocarbon knot strength is usually in the 74% range. So if you go up one size in you Spectra 40 mono with 50 Spectra , this approaches the rated mono, or Fluoro strength. The knots in Spectra are the weak link. That is not a bad but a simplistic solution.
There are many variables, hollow or solid Spectra, type of connection, ability of the person making the connection. Notice I did not use the word KNOT.
There are several connection methods in Hollow Spectra that produce a 100% connection of the actual breaking strength of the weakest material. Also was mentioned was heavier mono/Fluoro attached to Spectra might be tried. This is usually used as a leader application, and is best used for toothy critters, or abrasion. As you tie a hook/lure on the heavier mono the weak link is the Spectra connection. There is always a weak link. There are several great knots to tie hooks, etc. on mono/ Fluoro the one the wins contests is the one tied on the best piece of mono.
So I ask guys do you want a 100% knot at the hook? If so do you care if you loose 20,30,40 bucks of Fluorcarbon, or a two dollar hook.
Back to your frustration, Assuming you are using solid Spectra go up one size in Spectra Tie a double Uni with about 4 turns in the mono, and 8 in the Spectra. If that gives you a problem going thru the guides learn to tie a 16 turn Albright. A lift time and a very large book can be written on the subject.
Hope this rambling helps.
Thanks 4 all the info, Iím having a problem with the leader braking above the hook.