Plumbing question for fuel polishing and multiple tanks

[mcgann454]

I've been following some of the fuel polishing threads and have not seen my questions answered so I thought I would pose them here.

Situation:
I have two tanks each with two pick-ups at the top and a valve at the bottom forward part of the tank for a cross feed. The PO put a valve in the middle of the cross feed that I want to use to feed the polishing a system. The port tank has one pick up for the engines and one for the generator and the starboard tank has one for the engines and one open one that had a plug in it. The forward valves have a garden hose type valve that was open when I bought the boat. The fuel system has two racor 900 series filters and is valved to allow one or the other to feed both engines.

Questions.
If I pull from the cross feed and put a "T" with valves in to feed each tank, is it OK to put the returns in the second pick up of each tank or will back flowing a pick up cause problems?

Will it be a problem for the generator pick up to have the return go to it? Should I put a valve in the "T" for that to not pressurize the feed for the generator and only polish when the generator is off?

Why would you separate the two tanks and pull from one or the other? Why not keep the cross feed open so both tanks are equal all of the time?

Any other issues I might have missed?

Thanks in advance
Mike