A banner tow pilot on approach to a non towered airport reported they descended below low ceilings to remain VFR and flew too low over terrain and obstacles.

Narrative

During a VFR banner tow flight which was returning to ZZZ1 I contacted ZZZ Tower to request a VFR transition eastbound through their class delta airspace for a flight of two. 7 miles west of the field I reported 10 mile visibility and scattered clouds at 1500; although ZZZ was still reporting IFR conditions. I requested a SVFR clearance and it was denied. I turned around to delay and allow a third company aircraft to join our flight. 20 minutes later our flight issued another PIREP and requested SVFR clearance to transit the delta; but we were again denied. I chose to fly around the Class Delta airspace on the north side. On a 5 mile final to ZZZ1 Runway XX the ceilings dropped to 650'. With the banner hanging lower than the aircraft; I may not have had proper obstacle clearance approaching the airport. Due to the delays and change in route I had approximately 25 minutes of usable fuel remaining when I landed. To avoid this situation in the future; I plan to carry an extra 30 minutes of fuel; and take immediate decisive action when faced with unexpected changes to my planned route. In this specific situation; flying south of the delta airspace (over the water) would have been a better choice because obstacle clearance would not have been a factor.