The sucking air sound is the pickup being uncovered not the pickup threads having no sealer cuz the extra qt silenced it. You would need that extra qt to stop that & if that amt of oil is letting it happen now it'd be worse when running/shaking/vibrating (so you wouldn't want any less than that amount). Extra oil is more windage but the pickup getting uncovered is much much worse. The screen distance (5/8") from the pickup bottom is what counts not the flat metal "shoe" underneath it distance and the pickup/pan are rarely parallel & depending on how/where you measured it might be more than 5/8 and the distance of the highest corner of a tilted screen is the effective distance as it can & will suck air until the highest round perimeter edge of the screen is submerged . Short version: high perf oiling mods not withstanding (high perf build can have adequate psi but starve the rods (the end of the line/most important/critical area) if oiling mods ain't done) but if you have adequate psi for your mild build you are OK (use however many qts to achieve that) & no opinion on the suspended pickup.