My long ranger 170 tank is filled via a dual toyota filler with the pull up lever to divert to either The standard tank or the long range one.
No probs with the filling of either at all.
I have a small electric facet type pump on the outlet of the l/r tank ( switched from the dash) that pumps through a racor filter into the standard tank.
When I see the fuel gauge on dash dropping I just flick the switch & fill the front tank from the rear one, quite gratifying when driving to see the fuel gauge rise!
I generally put fuel into the rear tank & keep the front one quite full as this then goes through the filter before going into the normal front tank, good if the fuels may be a bit dodgy! Surprising how much crap is collected in the racor filter using this method.
I’ve also got a valve off t connection on the outlet of the rear tank that can then dispense fuel by gravity into a can or something& poured directly into the front tank if necessary, but I’ve only ever used this in reality to fill a new engine fuel filter when I change it to save a load of priming, quite handy from that point of view.
Andy