Why not add a 5-10 gallon "day tank"? I put in a 12 gallon Tempo tank to replace a 15 gallon Monel, and it's fine, and lighter as a tank.
You can put in a lift
pump and a return
line from the keel tank and gradually fill the day tank with "polished" and therefore dependable
fuel. Then you can fill the keel tank and just transfer as needed. The day tank can be gravity feed in a pinch.