… I have the same set-up and change my Filter as he does. And I think one Racor with Vacuum Gauge on top is ample. I change my filter at the beginning of each season. Keep an eye on the Gauge throughout the year and change if it starts to creep up. Having a dual system would be nice and redundant, which is good, but I have not had that need.

Also, I have a small shut-off valve in the file line just upstream of the Filter, that I shut OFF prior to making my change, so there is no spill, then back on after done. You should find a new gasket with each new Filter, I swap mine out each change. And, every week or two, I will drain off the Filter from the bottom drain maybe a quarter cup or so to get rid of any sediments or water trapped in the Bowl.

Cheers, John