Alberick

Just bought a Subaru 3 gauge dash pod to fit in my Blitz Power Meter ID.
Now, the question is, how to I fit this damn thing?? I can imagine where the pod goes in, but after fitting this large metal holder piece, how can I reinsert the top tray with the air vents??
I understand that I have to remove the top tray lid, which I did, but still cannot figure out how to refit it?
Do I have to cut something here? Anybody fitted this before and can give me some guidance?

thanks,
Ramon