The extra filteration by keeping the stock filter after adding a lift pump is only a good thing.
Usually the lift pump filters have a little better filteration over stock anyways.
Besides you can easily go with 2 lift pump filter changes to 1 stock filter change.
I'm not a fan of the Nicktain adapter and the Cat filters, I prefer to stick with using the RACOR PFF 50216-coalescer-fuel-filter, with the billet plug in place of the cheezy plastic water seperator.
Been running this way for over 5 years with my AirDog.