Limits of One Shot camera with a Light Pollution filter

So I've tested to see just how much detail one can capture before there are diminishing returns on my equipment.

So for me, that includes:

• Bortle 7/8 Skies
• SGO 6" f/4 Imaging Newtonian
  
• ZWO ASI 533MC Pro camera (3.76 x 3.76 micron sensor)
  
• Optolong L-Pro filter

I can't seem to improve details beyond 2 hours on small galaxies or 3 hours on nebula

Here are the results:

Draco Trio of Galaxies

Bubble Nebula

For nebulas, I'm receiving on Optolong L-Enhance tomorrow which will allow the Ha, Hb, and Oiii through.