Using a light aircraft such as a Cessna can be the best way to get your imagery if you need to cover a large area. Especially if your resolution requirements are not too great. In California you can use the local flight school at a municipal airport to buy an hour of airtime at a total cost of under $300/hr. This cost will be lower in other places and still represents a great value in terms of the amount of imagery that you can collect from one hourlong flight.
I like using rubber hand clamps. you can get them at your local hardware store, they are easy to use, and do not damage the aircraft. You always have to ask the pilot for permission, but that has never been an issue for me. But you should mention when you make the appointment that you would like to do aerial photography and you have a camera mount that you need to get the pilot to approve for using on the flight.
The hand clamp is nice because it is so universal. You do not need to set it up before takeoff. With a high-wing Cessna, open the window at altitude and then attach the hand clamp. Always hold on to the clamp while using it during flight. This is not only a safety measure (along with tying the setup to your person), but it is important to hold onto the assembly to dampen vibrations from the aircraft.