Fetteresso Forest 8 Miles
This involves driving to the start point where there is room for a dozen or so vehicles, you could run there and add on another 3 to 4 miles each way there and back from Stonehaven. It is a good route to run in all types of weather especailly good in the frost and snow as the forest tracks tend to have more grip. The forest tracks can be confusing though so I would suggest you run with a buddy the first time you do this one, or with someone who has done it before!