Just a suggestion - I used to have a '78 full size Chevy Blazer with the 6.2L diesel. After a few years, it developed a vacuum leak in the fuel system someplace - no visible leaks under pressure, but after sitting a while air would get into the system and let fuel drain back into the tank. In order to start it, I'd have to crank the engine a few seconds so the mechanical transfer would build up pressure in the fuel system, then open the hood and crack the fuel filter bleeder valve to let the air out. After that it would fire right up, but the after setting a few hours I'd have to repeat the process all over again.
This got old pretty quickly until I came up with a brainstorm. I cut the fuel line going into the fuel filter, ran a piece of 3/8" rubber fuel hose up to a 3l8" ball valve mounted in the grill and then ran another piece of 3/8" rubber fuel hose back to the fuel filter. When I parked the Blazer, I'd go around to the front and turn the valve off. Then when I wanted to drive off someplace I'd open the ball valve and the engine would fire right up!
Why not install a similar ball valve in the fuel line near your secondary fuel filters? When you check your oil level before starting up, open the ball valve, start her up and go. When you want to shut her off, close the ball valve and she shuts down. Makes a great anti-theft device as well!
If you really wanted to be cool, you could mount the valve in the cab in a hidden location. Positive fuel shut off, anti-theft protection, plus fuel drain back protection if you ever develop one of those mystery air leaks I've seen mentioned in other postings.