Looks the goods, youve gotta love it when a plan comes together. I have covered my axles in a puty/mastic tape, need help from other members here as I can't remember what it's called, but once applied you'll never have to worry about your axles rusting. How did you treat the areas where you appear to have screwed in the piping for your irrigation system as these are now potentially new rust spots.
Edit. Just remembered, I think it is called Denso Tape