Having just completed it over 2 days it’s definitely do able and I’m not really bike fit.Seen enough drainage ditches to last me forever right enough.Made it to tyndrum on the first day after an early start first bit conic is pretty easy once you get used to gates.Loch Lomond side I didn’t think was that bad just hesd down and keep walking soon disappears.
As said carry as little as possible think I had under 15kg of kit including sleeping bag and bivi bag.Lots of places to get food and water along the way so no point carrying lots if it.