After doing the 23 gallon tank, I should have just tossed the aux tank. Really never needed and made a complicated fuel system out of it afterall. Mine was setup as a transfer style. I ran a low pressure pump and accumulator (different that your setup with a built in high pressure pump in the tank). Mine drew off either tank, through the selector valve and into the low pressure pump. Pretty much like a standard carbed duel tank setup. Only difference was the accumulator only drained back into the main tank. This made for a little fail safe. If I forgot I was transferring fuel and ran the aux tank dry I only had the fuel in the accumulator left until I stalled the engine.
Made it difficult to accidently leave the pump on and burn it up running it dry.
With your in tank high pressure pump you won't be using the accumulator. Simplist would be a simple transfer pump. Trick is finding a way to shut it off once done transferring. And you need to be diligent in making sure you ran the main tank below half before transferring. All this leaves a lot of error potential for the operator.
There is the high pressure 6-port transfer valve that can work. Means adding a second (external) high pressure pump just for the aux tank.
I found I was using the aux tank so little after the big main tank I was having issues keeping the fuel fresh. I would honestly abandon the aux tank for now and see if the 23 gallon tank alone is enough. If so, take the aux out. If you find yourself needing that extra capacity, then figure out how to use it and bring it back to life.
