Yeah most tracks would be horrendous, but I think LR has a special niche for this. Im glad you noticed the shroom/tunnel idea. In shadows video it is shown the right side of the tunnel acts as a funnel. Timing the end of the outside wall with the music and then going into the grass gives a very consistent tunnel hit. Some tree hits though.
Clipping the grass to the right leaving the runnel, re entering the road, then continuing into the inside grass/sand gives a good idea for the second half, which I got lucky with on that video and kinda realized it last second. Was shocked I actually hit the shroom mt lol