Be patient with that. It will come. As easy as tunnels seem like they should be from our perspective, they have been vexing to Lily off and on. If she doesn't think about it far enough in advance, she ends up at the tunnel entrance, looking over the top of it and then she doesn't seem to realize she has to duck her head down (only a problem for a standard).
Lily AKC: CGC CD HIT CDX RN RA RE RAE RAE2 RAE3 NAJ NA; APDT: RL-1; CPE: CL1-R, CL1-H, CL1-F, CL1-S, CL1
Peeves AKC: CGC BN RN