"If getting run over is a preferable option. Cycling on the A82 is stupid."
The route doesn't take the A82 much after Paisley but the A814 through Helensburgh; A83/A819 past Inveraray. It uses the A82 between Fort William and the Erskine Bridge for the return leg by which time the riders will be well spread. I've ridden on the A82 many times myself and haven't found it that bad.
Andy Corless
I surmise that the route north will turn across the Connel Bridge (with no excursion to visit Oban). The route I've plotted (as far as Paisley for the second time) is 922km. "The south-bound route from Paisley back to Lytham is exactly the reverse of the northern route direction!"
https://ridewithgps.com/routes/28872782?beta=falseLytham St Anne's, Cockerham, Lancaster and A6:, Kendal, Shap, Lowther, Penrith, Carlisle, then //M74 via Gretna to beyond Abington, Kirkmuirhill west on B7806 via Strathaven and A726/A727 to Darnley, Paisley, Helensburgh, Inverary, Connel Bridge (N of Oban), Fort William, Inverness, Fort William, Tyndrum, Dumbarton, Paisley
Benderloch (@480km, just north of Connel) has a shop (and a cafe iirc), is 60 odd km from Inverary and you'd have 70km to go to Fort William, with only the last 20km on the A82 (some with cycle path).
Lytham St Anne's > Paisley 322km (D1 0800-0100)
Paisley > Inverness 324km (D2 0600-2300)
Inverness > Paisley 275km (D3 0600-2100)
Paisley > finish 322km (D4 0400-2100)
Assumes 19kph average during each day's riding.
Time in hand = 5 hours
Sunrise 0440 Sunset 2202, (almost new) moon till midnight