I've made lots of windons for game fishing and a few "double enders" for casting, mainly on lighter mono mainline. Windons work the other way round but its exactly the same principle. Double enders have 2 joints, one on the main line & one on the leader. The main & leader actually touch end to end if you do it right.
The serve is the weakest point but it does not have to be that tight. The hollow line "grips" the leader material because the weave "contracts" and the more force you put on it the more it contracts.
To get an idea of how little tension is actually required set up an incomplete leader/hollow braid without the serve and hold the serve area lightly between thumb & forefinger. Get someone to put serious tension on and you will see it will not slip. If it does then the leader is too thin or the braid too thick. The ideal setup as far as thickness goes is to have the leader close to the maximum diameter that will fit up the braid.
However if you push on the serve it may slip, so the weave no longer contracts under load. Pushing on the serve may happen as it hits a rod guide, or a rock ledge or obstruction out on the water.
When the serve is going through the tip guide under high tension (start of the cast) is when the serve is pushed so has exactly the wrong sort of tension on it. If it starts to slip at this point you will see the lure sail majestically into the air trailing the leader with a few feet of mainline hanging limply at the end of your rod, and you with the stunned mullet look on your face
It can also be a problem when handling the leader at the boat. You have to be aware of how it functions and handle accordingly. You can't let the leader slip through your hands so the fish drags the serve through your hands.
Its a good idea to roughen up the end of the flouro or nylon for the length of the serve, so even if it (the serve) loosens there will still be enough friction for the weave to contract.
What I do with the windons is to cover the area to be served with super glue and serve over the top. This makes a slightly stiff joint but with roller guides it does not matter. You will have to get superglue that will stick to the dyneama (or dacron) & flouro so it may take some shopping around. The same goes with casting as the pull should be nearly straight through the guides during this part of the cast. You can get special sticky stuff but I have never bothered.
If you are a bit paranoid, then put the whole joint under tension & put another serve 12 inches or so from the first. It should not be necessary & the purist will say it actually defeats the purpose of the first serve but it does take the pressure off the serve.