About 10' from the butt, you just need to get a running start in the DB. I hope it ends up deep in the tail out, and the current creates a nice trough under that root ball.
It will keep the sleds out until they cut it, last trip down, we had 7 sled all the way to the middle fork, in skinny water. I was anchored with my dad, fishing a skinny pocket, all sleds slowed to pass, but Swanny, and he ran full tilt boogie about 6' away. His wave left my boat high and dry on the gravel, and a deep bruise on my 74 year old dad's fore arm, as he crashed into the gunnel. We will meet again.....