Keep air within, but not without? Worldedit

Hi, I’m new to this site so I’m sorry if this isn’t the right place to post this- I’ve built an underground tunnel system of sorts, above ground. I used Worldedit for help. I want to bring this build underground now that I’m finished, but my dilemma is that I cant use //paste -a without the tunnels being filled. If I just //paste, the air within the tunnels remains, but the air between the tunnels also remains. How do I paste it so that the spaces in between the tunnels are filled, but the tunnels themselves are empty? Is this possible? I haven’t found an answer anywhere. Thank you!

 

@malimalibobali I believe that is impossible. You can probably get away with ignoring the spaces in between the tunnels if the user is unable to see them.

 

If you keep the tunnels itself empty and fill up the surroundings before copying it it should be working, or do I miss something what makes this impossible to do beforehand?