Rob,
You didn't mention the reason for your polishing thread. Is it sludge or water or both?
I personally am not a fan of polishing in smaller tanks such as sailboats.
I see you are in Maryland so your boat sits in winter awhile which doesn't help diesel.
My buddy has a polishing business & he is doing well. Most of his clients are larger powerboats w/gas and day tanks. He agrees that for sailboats, using good filtered fuel (clear like water) with no additives is the best approach, only if your tank is first sludge free.
For your tank, one way to fix fuel problems is to clean the tank itself with no fuel in it. I made a 6x6 access plate in mine, cleaned it spotless and only change out my filters once a year. I do however use a grade-a type fuel from a sunoco station close by. I never fuel up from a dock's tank. Another good tip is to remove any screen from your pick-up tube.
Polishing fuel is for removing mostly water from your fuel. If your tank has sludge, the polishing system will churn alot of it up, but not really clean the tank bottom. Hence the job is only partial.
As for winter layup, maybe you should drain the fuel. or, maybe keep the tank at near full to keep moisture from building up too much. People will have different takes on this, I know mine works for me, however I'm in Florida and sail year round.
Good luck, you will find the best solution according to your situation.
CR