Vacuum pressure switch for Barracuda?

Sorry to post such a complicated question as my first one, but it's what I need help with.

We have a large inground pool with solar heating and a Baracuda cleaner. We recently had a variable speed pool pump installed when our previous pump went bad. After two bad experiences in a row with different local maintenance companies hiring workers with a habit of billing for service without showing up, we have been doing our own pool maintenance for several years.

We have two automatic Jandy valves in the system. One selects flow to the roof solar heater, the other selects flow to either the skimmers or the Baracuda's dedicated inlet. They are coordinated by relays in the solar controller so that when it says the roof panels can deliver heat, the valves are turned to enable the roof and skimmers (for added flow); and when there is not (like at night), the valves bypass the roof and select the vacuum. (For anyone wondering, the main drain pipe was capped off by a previous owner for reasons unknown, and we've never changed that.)

As designed, the Baracuda operates only in a narrow range of vacuum pressure -- too much or too little, and it stops cleaning. Originally I attempted to set the stop limit of the Jandy valve to a point where it would not cut off the skimmers completely, so as to deliver just the right suction to the vacuum. The problem with that is that the suction is also affected by the cleanliness of the filter -- a clean filter can overdrive the vacuum, and a filter nearing backflush time can starve the vacuum.

I solved this somewhat by adding the spring valve included in the Baracuda kit to the inlet end of its hose, and setting the Jandy valve a tad higher. The vacuum then always got the proper suction because the relief port on the spring valve opens or closes to regulate it. But this diminishes the operation of the skimmers while not performing any skimming itself.

Now our new pump, at full speed (for serious cleaning use), can run both the vacuum and the skimmers; at the lower speed (for daily maintenance use), it can run one or the other. If I want to use the variable speed feature of the pump, setting the stop limit on the Jandy valve is no longer a useful solution, and continuing to the Baracuda's spring valve would effectively waste all the extra power the skimmers could be using.

My next thought was to detect the proper vacuum level directly by drilling some kind of vacuum sensor switch into the vacuum line, and having that stop the turn of the Jandy valve when the right suction is reached. That would always deliver the right vacuum flow regardless of the speed of the pump or the state of the filter. But at this point, I don't know if I'm on the right track, or just needlessly complicating an already complicated system.

Can anyone recommend a component that would do this job? How do other people attack this issue?