3D was INDUBITABLY the seed of this puzzle. I decided to try making all the clues four words long, and tried to balance some that were straight over the plate with a few that were trickier. How did it work out? I'd love to get your opinion!
These are just getting better and better! I grew up and lived most of my life in SoCal, so when I saw the name Rodia the Watts Towers came instantly to mind. Then, when I was in my 20's I was a paramedic in LA and while studying for the position we went over Sabin and oral polio vaccine and I wrote a paper on him. And yeah, INDUBITABLY was a great seed. Amazing puzzle, thanks!