The Sunlu S2 is a really good filament dryer. But it has a major design flaw: The hot air cannot vent out. There is simply no large enough opening in the top cover. Ok, I could just drill a hole in the cover but I like printing more than drilling…
So I made a gap spacer to keep the top cover a little bit open. This works suprisingly good and the humidity sinks under 20% during heating. The spacer sits flush on the bottom half and the cover just sildes in.

Print the spacer upright with PETG. PLA might get soft if the dryer is set to high temps. As it is a functional part use draft settings. No time to worry about the looks.
3 walls, 4 tops & bottoms, 10% gyroid infill and no support - see my 3mf file (Bambu Studio / Orca Slicer) for more details and my PETG settings.

Disclaimer:
This work by blecheimer is licensed under CC BY-NC-SA 4.0
You are not allowed to copy this model to other 3D printing websites without my permission.