Do you have a city feed for high pressure rinse or everything from the tank?I would add the third tank for consistency on your system. I always like to have the water in a tank before it goes out to the bays - easier to check the quality, temp. etc. of the water if you have it there right in front of you.
You should see the newest D&S stands. Everything is injected at the pump, spot-free goes through the pump, there are two regulators plus injectors plus all the usual solenoids as a traditional car wash put together in a way that almost nothing is serviceable. All this mess to not have tanks "to save space" that's now taken up by all the buckets and barrels around the stand.I have a DH millineum pump stand that uses exclusively pressurized feeds. The soap is injected using a Dema injector. There are no water holding tanks. I do not care for it, it is complex in comparison to the Coleman stand. Each bay has a pressure regulator and injector in addition to the solenoid. When the soap is not flowing properly you have multiple things to check.