Actually, I'm wondering if you were thinking of heading a bit further, perhaps on the track heading SE towards the southern end of Fionn Loch.
Here's something that's been pretty useful for me recently.
Geograph is a website where people submit photos for each square of the map. Type in the grid reference and view pictures taken with relevant information (camera position, direction etc). It is particularly useful in assessing whether a track might be bikeable. That particular path certainly looks interesting.
I know of (but don't own) Kenny Wilson's book 'Mountain Bike Scotland' which covers some very remote and challenging routes. There might be some routes into Fisherfield in there. If you're feeling brave you could also ask on singletrackworld.