[THEFERMANATOR]

All power trim system's I've ever seen were designed to be checked with the engine/outdrive fully trimmed up. The fill plug is normally right at the pump's pickup level so that when trimmed up your almost out of fluid to help keep you from blowing your ram out of it's cylinder(no pum intended ;)). This also helps to ensure that the trim and tilt system stays under pressure to minimize the chance of water intrusion into the system. If there's pressure inside that means fluid can leak out, but water can't come in.