Most importantly, this combo might be usable underground. HLaM + Living Roots + Rock Spike = Solo floor hack bullshit.
Actually, during the tournament, we want to always surface before using the rock spike. Its too good, we should keep it a secret.
Also, do we know what equipment we are limited to? Because sneaking in two full canteens of Chakra water would be nice. We pay Noburi through the nose, and drink it while we are hidden underneath the floor of the arena.
Incidentally, we absolutely must figure out if the floor can be traversed via HLaM. I recommend sending an earth clone the day before trying to tunnel from outside the arena to just below the surface. Or pay Keiko to use Panashe. The point is don't go in person, the might have laid traps, and it would be embarrassing to get caught.
If it isn't traversable, universal problem solving technique. Blast our way down, blast our way up. Incidentally, we need to practice that sometime. Maybe a 30-60 xp stunt to have blasting your way through the floor and getting underground only take two supplementals and a standard instead of two standards and two supplementals. (activate tag, throw tag, activate jutsu, move down).