I have also done a lot of mono to braid experiments. Braid and breaking strains is not an exact science, many break above their said breaking strain. To test one knot vs another, tie the knot to mono that will definately not break before the braid does eg 30lbs braid to 60lbs mono. I then cut the braid off the spool leaving it long enough to tie the same or a different knot on the other side, once again to the heavy mono. This means your end product has mono joined to braid, and the joined to mono again on the other end. If you tie the same knot on both ends, and the braid parts regularly outside the knots (more that 1cm outside), this suggests a 100% knot. Alternatively tie different knots on either end. The knot that parts is obviously the weakest. Of the well known knots pr is for me strongest, and fg 2nd. I tie a combo of the two. I also dont use a bobbin, but attach the braid to a sinker to do the spinning turns. The strongest join Ive found is a slightly different version of a bimini which is way to complicated to try explain. but this is more a backing than a leader connection. Ive been meaning to do a post on this, soon perhaps.