HISMC are spawning beyond their bounds

Hello friends.

I’m working on an engine tool to spawn a bunch of stuff and stack it in stacks (or on shelves horizontally). I originally spawned a bunch of child actor components, but I saw that HISMCs had a bigger performance advantage so I’m on version 4 trying to rain these joeys in. I’m using the same logic to determine the position of the object and weather it should or should not spawn, based on the mesh width and the box extents, works fine for CACs but not HISMCs. any ideas?

specifically, the meshes spawn as they should inside the box, and then sporadically with gaps between beyond the box.