I'm not Machka, but I am a former triathlete who used aero bars almost exclusively for over a decade. In order to get low, you need to have the handlebars lower than the seat by at least a few inches, and generally you want the handlebars further forward (i.e., longer stem or a time trial frame) than usual. Both of these modifications allow you to stretch out over the frame and keep your back low to reduce the frontal profile into the wind. Of course, these modifications probably won't be pleasant on a touring setup where you generally want to sit even more upright than on a road bike. Putting areo bars on a regular touring setup will still have some areo advantage, but you're going to be much more hunched over the bike and will be unable to "get and stay low."