Knot Recomendation

[pacrags]

I have 10 lb braid on a few of my rods for trout fishing that I have been tying on a swivel and then a 4 lb flouro leader. When my kids use this set up they keep reeling the swivel in through the guides causing them to tangle up the line at the tip when they try to cast with the swivel among the guides.

I have been trying a few knots (yucatan and modified version i used to tie heavier mono backing to the braid) to tie the flouro to the braid but the flouro keep slipping through the knot or breaking when i cinch it down.

looking for some suggestions that work for oothers with this setup.

Thanks in advance.