Thanks for the response. First time posting so I wasn't sure which settings would be important. You did a great job with your assumptions. I am using Chep's (assuming you know the name but otherwise irrelevant) Magic0.12 settings as my starting point, though I have tried with default Cura settings as well.
I have printed my model and that is where I first realized the holes being left. I print in white PLA, paint the model black, then sand the tops of the letters to get them white again. Since the paint seeps into the holes/cracks, that black always appears.
I was able to make some headway by simply reducing the wall count to 1 as you suggested. I tried with and without ironing and it didn't seem to make much noticeable difference. The sliced images shows a lot more of the letters filled in, but you can still see gaps at the top and bottom of the 3, bottom and middle of the 5, and top of the 2.
And after I painted it and sanded:
...you can see these spots on the resulting model. (Sorry for the picture quality.)
I have downloaded the Cura version you suggested and will give that a try. But I'm guessing that I may need to use a smaller nozzle (.1 or .2) on my printer to reduce the line width so it can fill in those small spaces/gaps/holes... 😁
I've attached the .stl file for reference. If you have any ideas on other things to try, let me know. I'll report back after I have installed and tried the other Cura version.
5-Speed Shift Plate 2.stl