What race car - ever - was built to carry unuseable fuel?
In SPF's defense they couldn't do what the "originals" did which was rubber bladders that are not suitable for street use. So they supply stainless steel tanks that slide into the "sponsons" with an outlet on the rear of the LHS tank. So far so good.
But they also have to cross-connect the tanks. Since the bottom of the tank is curved, either the outlet or the cross-connect is going to be higher. Thus fuel gets left behind no matter what you do.
Unless....
If you were starting over and wanted to make sure this problem did not exist you would provide
only the existing outlet port on the LHS tank and then "tee" off of that to supply the fuel pump
and the opposite tank where you would also connect
only at the bottom (inside) of the tank. Problem solved, but with a little more hardware (i.e. the tee).
However, I suspect the reason the crossover ports are "up" on the outside is to ease the bend radius of the 3/4" armored hose as it turns to go through the bottom of the engine mount. Of course if the crossover were made of metal tubing or used a hard eblow it could have any bend radius it wanted, so that issue would go away. But as it is they are about 1" higher, which is about 10% of the tank capacity. At that point the optimistic designer might think that with some spirited up and down and left and right the fuel would all get sucked up, but obviously it doesn't.
What I did, and I don't recommend this to anyone, is to add a second outlet port at the bottom of the
front of the RHS tank, and draw from that with a second fuel pump. So now I'm drawing from the bottom of both tanks, and thus get all the fuel and don't get any fuel starvation when going up or down hill with low fuel level.
In fact the
latter issue was the nominal reason for all that work. But I now have a vastly more complex and expensive fuel plumbing situation than what SPF supplies. And frankly, the whole exercise was kind of silly because a) the last gallon or two of fuel doesn't really hurt anything and b) just keeping the tanks mostly full prevents the hill starvation. But others have put in swirl tanks for the same reason.
And then of course I made an elaborate crossover tube from 3/4" stainless tubing neatly tucked away where nothing can damage it and then relocated the crossover port on the RHS tank to the inside/bottom.
This whole pile of irritating fuel system issues was kind of my Mt. Everest (or windmill to be tilted). It was
there so I "had" to climb it. But it's also why my car still isn't running.... So you choose your battles and sometimes lose the war.
New license plate idea: "PHYRRUS" or "QUIXOTE"