Good question. Hook a pressure sending unit up to your data logger and see what the numbers are. Personally I don't trust a pan evac system to do much of anything. If the engine had a vacuum pump then I'd go with a metric ring pack. We've used the Mahle 1/1/3 mm ring packs and they free up some power that is for sure.
No running motor at this time, just some pistons with .043/.043/3/16 ring pack. I have considered what to do with the megablock that i split a cylinder in. Fix it, or sell it and a potential buyer doesn't use a vacuum pump. The pistons and rings in seven cylinders only have seven runs on them, and could be built pretty reasonably for what he wants if the .043 rings will work.
