^^I have the same unit (25-71). $479.99, new/delivered from Agri-Supply. It's mounted on my ATV. I'm getting 60+psi, now that I figured it out. I broke the wand that comes with it on day 1. I'm kinda glad I did. I replaced it with a really nice unit.....got rid of the 15' section and added a 25' section. Great move. I admire the OP's ingenuity. I'm anxious to see if he can get it calibrated. Good luck. I hope it works out. And, I hope you'll continue to post how it's progressing.