For what it's worth, I added the drain hoses to the bottom of the pans on a boat a couple years ago.

One motor was out for rebuild, so we drained the one that was still installed with a vac pump via the dipstick. When we pulled the drainplug, there were only a couple of drops that came out. As long as your dipstick goes down to the bottom of the pan like it should the vacuum pumps get the majority of the oil out of the pan.