Awesome photos... thank you so much for laying down there and snapping those. Really helps me visualize how you surmounted some thorny problems.
TransferFlow in Chico CA used to be the go to company for fuel tanks in Ford Chassis cabs, at one time offering a 30 gallon midship, a 34 gallon midship, and a 50 gallon midship... all available for 176" wheelbase crew cab narrow frames with a 60" cab to axle distance. Transfer Flow also offered a larger volume replacement aft axle tank, because so many of the stock steel tanks were delaminating due to the interior lining that Ford coated them with that was chemically incompatible with ULSD, and Ford didn't figure it out until some time after the fuel change over... however much time it took for the coating to delaminate and clog up the fuel filters, bringing in truck owners exasperated with a loss of power.
But TransferFlow suddenly exited entirely from the Ford chassis cab replacement and chassis mounted midship fuel tank business. I suspect one reason is that darn DEF tank that you had to work around, and the reticence of commercial fleets to change anything that would effect the original factory warranty on such an expensive engine and fuel system... leading to a loss of demand and a collapse of the market for chassis mounted fuel tanks. There is no easy solution, because mounting the tank outboard on passenger rail forces a flat bed only type of bed. No service bodies. Moving the tank isn't just moving the tank, it is moving the specialized heated injection lines for the DEF that keeps it from freezing. Ford only approves two locations, neither of which are optimal for a mid ship fuel tank combined with a service body. I couldn't imagine how you got it done, so I'm thankful for your photos that show how Aerotanks utilized the much shallower space directly under the cab, pretty much at the break over angle between axles. Yet, it appears from the photos that ground clearance is no different than say, the stock running boards.
I had forgotten all about Aerotanks. I don't have DEF in my 7.3L 550, so I had planned on buying a Transfer Flow midship, but they not only no longer have any tanks in stock, they flat refuse to make any more. Not unless you are going to order and prepay for a large volume. Even though their website says custom orders for 5 or more tanks accepted, Randy Gaines personally said that he wasn't interested in building them any more. This is sad, because for 15 years or so, Transfer flow was the preeminent fuel tank company that built tanks for the Ford narrow frame chassis cabs, including the Ford F650 SuperCrewzer and the Fontaine Classic Traveler (Ford approved ship thru modifications), as well as Gary and Monica Westcott, in their Turtle V expedition camper. Tow truck companies who were dissatisfied with Ford's measly 19 gallon and later 28 gallon midship tanks turned to Transfer Flow for their larger 34 and 50 gallon midship tank, because tow trucks delete or never order chassis cabs with the stock aft axle tank, due to wheel lift equipment interference.
Guess I'm just rambling, but your solution was quite interesting. With your midship tank directly hard bolted through holes drilled through the flanges of the truck frame, it will be interesting to see how it handles the frame racking next time you go off road, with your new super single wheels and tires emboldening you to "Go Further", as Ford's marketing mantra encourages. I noticed the reinforcement side plates welded on to the tank sides supporting the mounting brackets... but as a reader of Expedition Portal, seeing all the builds with the sophisticated flexible camper mounts to accommodate frame twist and prevent crack propagation... I'm sure you put a lot of questions to Aerotanks about choosing this type of installation over traditional straps... and I'd like to learn more about how they warranty a mounting system like that, and how the tank is supported on the driveshaft side.
