Aren't the Ford capless fill tanks equipped with the anti anti-siphon barrier? I don't think you can just stick a rubber hose down the fill tube. I'd be more concerned about someone taking a metal punch and poking a hole in the actual tank (if the anti-siphon mechanism exists).
yes there is type of lock on the flap thats why they provide the funnel in order to use jerry cans and put it additives. if you look at the hole there is two tabs on ether side that need to be pushed in to allow the flap to go down. this next part is take right for Fords web site. "With Easy Fuel, the spring-loaded flapper door is held closed by two latches that can only be released by a standard-size unleaded fuel nozzle. When the proper nozzle is inserted into the filler neck of the system, the latches release, and the nozzle pushes the spring-loaded flapper door to the open position. When the nozzle is removed, the flapper door automatically is forced closed by the spring."
"Easy Fuel also has a patented mis-fueling inhibitor to reduce improper fueling and siphoning.
The inhibitor consists of a fuel nozzle detector that guides the nozzle to the opening. If a nozzle or foreign tube of a different size – a diesel nozzle or plastic hose, for example – is placed in the filler neck of a gasoline-powered vehicle, the latches will not release. For a diesel-powered vehicle, the inhibitor will keep out the smaller gasoline nozzles.
To protect the fuel filler neck from dirt, dust and debris, Easy Fuel relies on a flexible rubber seal in the body housing. The system also comes with a handy plastic funnel, which is stored with a vehicle’s tire changing kit, in case someone runs out of fuel and needs to add a gallon or two from a portable container.
“Because fuel cans are not standardized in terms of their nozzle, we needed to make sure customers could easily get fuel into the system if they ran out,” said Aitken. The funnel is the same diameter as an unleaded fuel pump nozzle for a gasoline-powered vehicle. "