My feeling is that the steeper the slope is, the more (closer together) swales, the less the danger. The more water you can get to soak into your soil, the less there is to accumulate in the swales. Too much concentrated water in the swales is not only added weight, but also, possibly more water than the soil under the swale can hold. Liquified soils are much more prone to (downhill) movement.
A good topo map is handy for laying out a plan. Go here:
http://mapserver.mytopo.com/homepage/index.cfm and locate your property. 'Pretend' that you are buying a map. Once you have "your purchase" set up, you are offered the opportunity to preview it before giving them your CC information. Bookmark
that page, and download the image. You can now print out as many copies as you need to devise your plan. It is a very handy tool for overall planning of your site.
Good topsoil it too valuable to be giving to your downhill neighbors (not to mention the liability issues!).