My preference is a single line system with the swinging p/u in a dragster style pan with trap doors ETC. Never lost pressure, or had an oil starvation related failure with this system, but 7550 is max I've been.

Had a dual line system, and suffered from it losing prime if it sat a while. An old timer told me after hearing me complain about it, that I needed to replace or rebuild the pump. He was right, after replacing the pump, it quit doing it, but I've never had that happen with the single line system.