i've always understood it that you never want filters on the suction side of the fuel pump, the suction can collapse the filter media and cause starvation problems. always filter on the pressure side.
I had a filter on the suction side by the tank and it was causing me all kinds of headaches that went away after I got rid of it, and moved to a filter just infront of my regulator.
This pic here
isn't the greatest pic for this, but you can see my regulator and filter setup, all mounted by the carb on the passenger side.