I generally use maxima for leaders. Different diametre depending on what or where i am fishing.... If you say leader to hook let's look at the first part of your question... Your leader doesnt go straight to your hook, that is your trace... Unless you are talking about lures?
8kg is extremely light, but i havent used kg in years just diametre. I moved away from the clinch knot years ago for the same reasons. I use a 3 turn uni knot for everything. U basically end up with a "hangman's noose", with the tag end lying flat against the line. When I tie a leader to braid, i use the exact same knot, on thinner nylon i use 4 turns and on the braid side between 7 and 10 turns.
Once you get the hang of this knot i can tie it very vast even standing on reefs in rough water.
So if we are talking about leaders:
.45/50 leader on my 20lb braid
.60/75 leader on my 50lb braid when fishing sand or reef but only smaller reef species
.75/90 leader on my 50lb and 80lb when fishing reef.
Triplefish makes a coated or very hard mono leader, not their fluro one. It is in some of the Sportsmans warehouse, don't know if one can still find it. I fish the .75 on any of my heavier gear, and have fished very nasty Southern Cape areas, and landed a decent fish here and there. I don't use it all the time as I havent seen it around and only have a little bit left, but I have on occasion fished Gouritz for a week with the same leader I arrived with. I sometimes up it to the .80, and use the .75 as trace line especially if fishing for crackers.
With all knots, you need to add the lubrication when pulling tight, and do it slowly, keeping the knot neat. I have found the times when i test and snap off usually one of the coils of the knot did not line up next to eachother but over one of the others.