A belated thank you for posting this, Owen; I'm making a brief foray into the Glen Feshie hills this Friday (15th), and your trip report is most interesting.
I'll be setting off early afternoon as I am driving down from Orkney that morning, so I'll not be walking as far as Monadh Mor. If the weather is half decent, I'll be climbing Mullach Clach a' Bhlair from Achlean, continuing on to remote Coire Mharchonaich before following the River Eidart down to upper Glen Feshie, where I'll camp for the night. Back down the glen on Saturday, and then away to pick up my son in Glasgow!
I'll post a report if all goes well.