Gary, only 3 of your slides are hydraulic which is why you have only 3 “in” solenoids and 3 “out” ones. If your bed is streetside, it’s slide mechanism is probably electric. The solenoid pairs are usually numbered #1 streetside front, #2 curbside rear (commonly a hydraulic scissors slide), and #3 curbside front.
Thanks for the heads up on the “flipper” valves. I hadn’t heard about such an animal. Doesn’t sound like they’re anymore reliable than the release nut ones. We’ll have to check HWH’s website for more insight I reckon.
Joel