Since you mention how plants look on slopes, this is an opportunity to plant those with drooping habits and hanging parts that don't look good or show well on level ground.

Reading your Member Page helps to frame an answer. I am certain that Toronto has a city forester. This should be the first person with whom you consult to guide you in clearing unwanted undergrowth, thinning young saplings and protecting mature decidious trees. Further, the city may have some rules concerning a ravine that conducts water to Lake Ontario. There should be no charge for this service and you may find many of your questions answered. Foresters have knowlege of native plants plus the ability to work with your original designer, Mother Nature, and can advise the best methods to deal with sandy slopes. Also might be able to provide the name of a designer who understands your situation with whom a consultation might be in order.

Try over on the hillside gardening forum too. One thing to consider is composition. Think of the whole more like a painting, because that is almost how it will be viewed, vertically. Many shrubs and trees have a beautiful structure that view people see because they are usually above it, looking down. On the downward slope, you have the advantage of being able to plant larger growing shrubs, because you will always be able to see over them. Is erosion an issue yet? You need to plan on a path for water, because it will cut through the hillside quickly. Enjoy your privacy, steep hills are great deterents to unwanted visitors.
NN

I'm not a designer, but a very famous one once said that given the choice of sites out over a downslope or sites with a view of an upslope to create a garden on, he would choose the upslope because it would display his plantings so nicely. This is an opportunity. I personally also love properties set above one's neighborhood because they offer privacy plus a nice outlook. Have fun!

healthy mugo and black pines look good from most angles

sabi