The first part of this route (as taken off the TomTom and viewed in Tyre) is the A86. Superbly surfaced with grippy overlay on the bend. In the dry it must be superb. In the on-off wet it was still pretty good.
It is clear from this view that the loop top the east to get to Balmaha was a lot longer than the west back of Loch Lomond route.