I have the same tank/stand combo. It was my old system that was shut down when we upgraded this past summer. Still trying to decide if I will set it up again or sell it but anyway that is not the topic.
Good call on getting a custom sump built, the marineland sump normally supplied as a set is really a poor design.
As to the air hose on the top, discard the one that came with it and use a longer piece of air line. The short one will make all kinds of noise.
Looking forward to seeing it set up
and if you need any info or run into any snags with it just let me know, will do whatever I can to assist.
Cathy