Loads of good advice and experience sharing here. I'll simply add our own experience. We currently keep one drake with five hens, but it requires management from about now through September (we live in Maine). For us, the domination issue is a bigger issue than the actual mating. Our drake will often pick one or two girls that he wants to dominate but not mate with. This manifests itself in him running them down and standing on them, so we keep him separate from that girl or girls. During the "off-season," he's fine with them.
When I say management, what I mean is that we need to be vigilant when they are all free-ranging together (which they do at least 2x/day), and we need to be set-up to separate the flock during the day and at night. In terms of separation, we still want them to all be together and be able to see each other. We have two fenced pastures for daytime use, and we have a separate fenced area inside the run for nights. We generally separate them in groups (no duck is ever alone), and we mix those groups up so they don't form "separate flocks." Interestingly, our drake can be with his favorite girl alone all night with no problem. In fact, she often runs into that area first when we put them in at night.
It was not our experience that the first year was the worst. The third year was probably the worst, but that was also the first year (I think) we went to a 1:5 ratio. There are so many variables. The only truly good advice that probably applies to everyone is to make sure you can easily separate your flock if you have a drake (both during the day and in a predator proof scenario at night).
Good luck and keep us posted!