"ahhhh grasshopper, it is faster to pit twice then it is to run out of fuel we have learned"..........haha.
An extra fuel filter most likely wont be enough to add more then a few seconds, maybe 10 or so, which in my opinion is still WAY too close.
I pit at 6 minutes if it runs out of gas at or about 6:30-7 minutes. I pit at 7:30 if it will go 8 pretty easy.
I always try and keep a 30 second or more cushion, since running out of fuel never wins a race and there are too many variables.
The only way to add any real fuel mileage is to turn down your high end point and reset the high needle to keep the engine running crisp up top at less then fully open carb settings. Just between us it also helps with lap times by eliminating alot of excess wheel spin with high HP engines..............