Very good! My decoder bracket also has very small clearance over the worm. 0.020" sounds about right. I didn't remember a problem with that oil bunker screw, but upon reviewing the photos I see that I did.
My solution was to slightly countersink the area surrounding the screw hole (visible at the bottom of the photo below). That way the screw head can be screwed slightly deeper, just clearing the microcontroller chip on the decoder.
If I was going to install a decoder now, I would probably use the
DZ156T DZ126T mounted on the side of the chassis without a bracket (like it was mentioned an an earlier post).