You said "only slight" marks of pellet hitting silencer.Any type of collision will send pellet way off course. I found the best way to silence a CP88 is to fit the 6 inch barrel which protrudes 2 inches from the slide and fit a proper silencer using a barrel bushing.Very quiet and accurate.
If you want to stay with your current setup, you can put a slightly larger diameter drill down through the silencer to make the bore larger for clearer path for pellet.
Baz