In reply to JLS:
Fair point. We got the ferry over from Inversnaid to Tarbert and then headed south so not familiar with the northern end of the west side of the loch.
If it's any help here's the route we took over 2 days
https://www.strava.com/activities/945308987 (anti-clockwise)
I was on my hybrid, daughter was on her adventure road bike, so not really any mountain biking, but otherwise a route I'd recommend . Camped just north of Luss using the new NP camping scheme
Hope you have a great time there.
Dave