Hi
teh route I did was almost all on sustrans / estate roads. Callender to killin on sustrans, old railway with towards crianlarich, road then WHW to Tyndrum and glencoe, either devils staircase or round by road to kinlochleven, up past mamore lodge and loch Eilde nor to Loch Treig and on to corrour along loch ossian and then north to loch laggan, along locan nan hearba to laggan, road to dalwhinnie ( possible singletrack shortcut we didn’t take) and then Dalnaspeil lodge and glen garry to kinloch rannoch
If its any good to you email me and I can send you more details