1968 Barracuda Notch 340

enough slope to side fill, also not enough to stop fuel running out on right hand bends unless the cap is a sealed one (not a breather cap). i totally get the rear view, but the spare tyre well's still there so having the tank no lower than that would be no different. i really think the filler tube angle will cause issues cornering, but you knew that already as you'd fitted the check valve. and as i said before you can't fully fill the tank as it is. your car, your call.