My understanding is that the pickup should be no less than 0.250 at any point from the bottom of the pan, and ideally at a slight angle to the facing pan metal. (E.g., the clearance should taper from about 0.50 to 0.250.) If it's perfectly plane to the pan surface, about 0.375 is minimum.
Different setups have different requirements. Your pan should be baffled or gated to keep the pickup deep in
oil in any case.