'lowest pressure components can handle' I take it to be the rated pressure of a component, ie the operating pressure. And although the rules say so I'm almost sure that most of the custom built rams and valves which are operated above their rated pressure are not independently tested. This issue has been discussed at length a couple of years ago and from what I gathered it seems that the event organizer has the final say, so they might accept a custom built HP system which was not pressure tested if they deem it well built.

As for solenoid valves, most are rated at 8bar but will handle more pressure. It's not going to explode, but it might leak at the end caps where the pilot valve is.