I am running a CL-44 Synergy sump and I have two 4'' filter cups built in and I was wondering would I be able to fit two of these Di-4 Drop-In Fleece Filter Systems in my sump?
Hard to tell from your photo but the one thing that might be a problem is the motor might be obstructed for the rear unit from your drain pipe. The units need to oppose each other in terms of the motor if that makes sense.