Strategy For Collision For Colonnade?

I’m trying to create a custom collision mesh for a colonnade structure, so the character can walk among columns but not through them. The columns are fairly realistic scale and not monumental. While I’m not having trouble creating the blocking mesh, or exporting it, somewhere in the export/import process it gets reduced to its most simple bounding box. Needless to say, this prevents walking among the columns.

I’ve tried making a series of tall, thin boxes, combining the meshes in Maya and going from there. I’ve tried making a single mesh, adding edge loops and extruding where the columns go. No matter what, I get a collision structure that closes off the area between the columns.

Any ideas where in the process this is happening? Any idea on how to prevent it/make an effective collision structure for such an environment? I’ve got a few hundred columns, so I’d rather not make them in Unreal directly…

Thanks in advance!