With an HOB I am not sure.
What you can do is create an overflow box kinda cavity to fit the HOB with gap at the bottom for the suction.
But for the canisters you certainly can make holes for the pipes to fit in.
Here is my custom made Universal Rock background in my 265. Since the tank is 84" long I had to join two 4' sections together and then add a 6" filler strip across the bottom since the tank in 30" tall.