DJN
Log into mapometer.com
Register, it's free, and play with the mapping tools. They are quite intuitive.
Based on what you've posted above I've mapped out a 9.5 miler on what look like forestry tracks, starting at a junction on the Rhigos road. . The way I've drawn it looks like it ends with a short descent then a road descent. Far better would be to climb on the road to warm up, then a net descent to the finish line!
Here's the saved route. It's just a taster, but if you zoom into the map in "hybrid mode" you get to see the topography and the tracks are still mapped out.
http://www.mapometer.com/mountain_biking/route_1932028.html
At the top left hand corner of the map is a "Search for other routes in this area"... give that a try. (Edit, forget it, there aren't any!)