So based on the very informative comments thus far, IF by chance the LP pump(s) is insufficient to meet consumption demands with the regulator on the very free flowing -10 return line (and subsequently producing a negative pressure in the pot), then I'd be better off with a "very restrictive" but open return line that would allow air to be drawn back into the swirl pot, thus allowing the HP pump to work efficiently. The "very restrictive" return line would provide some pressure rise in the swirl pot duirng times of low consumption.