Enlarging picking volume

Is there a way to enlarge the bounding volume on a Mesh (or Spatial) in order to increase “tolerance” for picking? I have some small objects that would be a pain to click directly, so I want a collision to occur whenever the click is somewhat close. I tried something like:

sphere = new Sphere(16, 16, 1f);
sphere.setBound(new BoundingSphere(3f, Vector3f.ZERO));

but this seemed to have no effect on picking (i.e., still have to click directly on the sphere.)

I could add a second, larger sphere to the scene graph, set it to always cull, and collide against that - but that seems like a wasteful hack.

Picking is done on the mesh level, not on the bounding box.
the bounding box is used for culling, so I recommend you leave it as it is.

For your issue, the quick and dirty solution would be to have an invisible bigger box surrounding your object and following it.
attach your geom to a node , attach the box to this node too place it so that it surrounds your geometry, and set the box cullhint to always so that it’s never rendered.

Else, maybe shooting several rays around the mouse position could get you more chance to hit the geometry, That’s not 100% guaranteed but It would be less dirty than the ghost box.