I'm with Kristen and just fit as much of the border in the hoop as possible at a time, keeping the tension fairly loose then same as for the rest of the quilt. Tedious moving it that often but I've been too cheap to buy an edge hoop.
As to knotting at the end, I just wind the thread around my needle a couple of times to make a knot, then bury it in the batting and pulling it through making the quilt pucker. I then clip as close to the top as possible and when it smoothes out the end is not visible.