The sump is barely too big to pull out the front and replace with a custom made sump. I would have been to cut off 3 to 5 Inches of the current sump to remove...
I have not found a modular sump that I am happy with but do have a 6' acrylic display tank that is as an original premium aquatics display tank before they moved to Edinburgh. It was the best sump I have ever had for a 180 gallon, but won't fit unless I cut and reglue multiple times whitch is considered, but would rather find a company that designs a worthwhile option .
I have had custom done by Bashea on the past but had to "Fix" a leaking bio reactor per his replay, order a new lid since he sent a 3/8 and I plumbed for a 1\2 inch per advertise and was told that people run to much water through them and then free shirt after $3000 dollars (not requested) was printed with the logo on the back... not real impressed with quality control...