Size and Align BSP to Actor?

I’ve several actors grouped together to form a single wall. I’m wanting to generate a BSP that’s the exact same size as the wall and align it with the wall as well. Is this possible? As is I’ve to manually keep re-sizing the BSP until it LOOKS like it’s the same size, but it’s so hard to tell. Any advise is welcomed. Normally I’d just combine the meshes, but they’re blueprints and for some reason combining the blueprints doesn’t combine the meshes and I’ve no idea how to extract the meshes from the blueprints so I can combine them either.