Collisions with terrain bounding box using Spatial.findPick

I'm using Spatial.findPick with BoundingPickResults  for a rocket's collision avoidance and acceptance (explosion :)). When the ray's origin is in a valley of the terrain, Spatial.findPick reports that the ray is colliding with the terrain because the bounding boxes for the terrain are covering it.  If the launcher is below the highest point on the terrain, the rocket explodes as soon as it is fired.

TrianglePickResults works fairly well but I would rather not use it since it limits my active rocket count to around 10 before everything comes to a standstill.

Any recommendations?