I think the screen will have some effect, almost like a windage tray. IMHO I wouldn't run without one, at least with with any sort of stroked motor. We have a 5.0 stroke 655 that basically runs the same pan and oiling system as our 572 (4.5 x 4.5). The pan is custom, long length but shallow for ground clearance. We couldn't swap over the windage tray that we use in the 572 for obvious reasons so we ran without it in the 655. We used to lose oil pressure in the shutdown, it didn't drop to zero but it used to get low (down to 15psi). At idle, hot it's around 45psi. This never happened with the 572. We also run an accumulator. Bearings looked fine on strip down, we didn't do that many runs that season anyway but we are getting a custom tray/scraper built. I see it as cheap insurance on wet sump systems.