This concept was utilized on my 1972 Krogen trawler. Originally it was a gravity fed 2 gallon float controlled tank that fed both mains and the genny. There was a pair of 900 racors that could be switched from one or both tanks. It had a transfer pump on the lower tank to move fuel into the supply tank. The tank was stainless steel and mounted on the center bulkhead. The main purpose was to return fuel from the engines to the small supply tank, thereby limiting returned heat from the mains (detroit 4-53s) to the large tanks, lessening the load on the AC. It worked great. I have improved upon this concept by adding a larger and calibrated tank for each main and the genset. I can tell in one hour exactly how much fuel any engine uses. I have two 750 gallon bulk tanks and two 125 gallon secondary tanks, all 5056 grade aluminum (that was $$$). The fuel from the bulk tanks is filtered (30 micron) befor it goes into the secondary tanks and filtered again (2 micron) befor it goes to the supply tanks. It is filtered again befor it goes to the engine filters. The bulk tanks are plumbed into an RCI fuel purifier with a 1/3 hp 120 volt circulating pump for polishing. The secondaries have filler holes but they are only accessible from the galley/dinette floor hatches. Ideally they only get filtered fuel from the bulk tanks. The fuel lines from the bulk tanks are 1 inch npt so I can fill the secondaries pretty quickly if needed with the circulator pump. Every baffled chamber is accessible through floor hatches, in all tanks, water and waste included. A diesel powered boat has three main culprits that will stop it, fuel, fuel and fuel. I have backups designed in for most things but I am really anal retentive about fuel.