I'm certainly not an expert, but,
what do you think of this as another simple method for installing a diesel fuel return line...
Remove the inspection plate from the top of tank and install a proper fitting on the plate and re-install.
And be sure to use the right sealant on fuel tank fittings. I used a silicone-based sealant to bed an inspection plate on the aluminum diesel tank I'd installed in our last boat. The sealant turned to a slimy gooo within a few weeks. And I immagine a few gobbs found their way into the fuel, which could have wrecked havoc on the fuel pump & injectors, were it not for our Racor.
I'm also told that it's important to keep the hot return fuel away from the fuel pick-up point, to prevent heat build-up, I suppose.
While on the subject of fuel systems... the first time I put fuel in our last boat - the bilge pump immediately sprang to life and created a big problem, which required a big clean-up effort and surgical removal of the tank. Not an Easy Job. I found holes in the bottom large enough to put my finger through! I replaced the tank with a new one in Hawaii - at great expense. The new tank required later removal in Australia and Guam during the next five years because of pin-hole leaks which kept spring in the bottom. Corrosion problems persisted until I replaced the bonding wire. The next five years were leak-free. The core problem was solved with three bucks' worth of wire & two terminals.
Our new boat came with Stainless Steel tanks and the fuel hoses were sticky & nasty. It cost over a hundred dollars in materials to replace ALL hoses & clamps with "da kine". I also installed a good electric fuel pump and mounted the switch where I can reach the bleed screws, Racor and switch from one location. And I painted the bleed screws yellow while I was at it. Maybe I'm being a bit anal, but now I completely understand my entire fuel system and hopefully, will never have to think about it ever again.
I'm sure there's a value for Peace of Mind... especially on a dark night at sea.