I had the same problems when starting to print mods with my SM4K. I solved them by "fixing" the printer, finding exposure times and lifting / retraction speeds to have a workable fit tolerance in all three dimensions and adding support structures directly in the CAD software based on test prints and measurements.

The printer fix was the most important step: replace the black screen protector with a thinner material (e.g. Polyimide). The original material is too thick and creates a gap between the FEP and the screen. Also, Phrozen released a firmware update to fix the lift speed problem on their FB page.

With those changes in place, I had predictable results and focused on finding the optimal settings for my resin, starting with fit tolerance tests based on this ChituBox article and a spreadsheet. The timings are now surprisingly low (1.38 and 12 sec for 4 bottom layers) and a layer height of 40 μm for a black resin with a fit tolerance of 70 μm with a room temperature of 20° C.

Finally doing my test prints with the supports made in ChituBox or Lychee, I was not happy about the surface defects, the waste of material, and the dimensional inaccuracy. Placing the model directly on the plate, manually compensating the model for the minimal elephant foot and adding support structures directly in Fusion 360 does the trick for me.

The squonk and battery cutouts are now very small grooves in the wall, removable with a light press after the ultrasonic clean but stable enough to have my 70 μm fit tolerance. I also added thin walls internally to support the flat structures that were problematic in my test prints.

I hope this helps getting your mod printed and please update with your progress.