What if anything are you going to do in the small overflow chamber where the emergency overflow drains? (just as there won't be much water circulation going forward)I removed the vertical glass panel parallel to the front of the sump that separated the two filter sock inserts (the one that has a slot for the refugium baffle). That one had to be removed to attach the drain hose.
I left the vertical panel that is perpendicular to the front of the sump where the drain pipes drain into the sump (the bubble trap all the way to the right side of the picture). That piece could be removed but I didn’t find it necessary unless the reef mat is being installed immediately next to the downpipe as pictured in post #21.