Starting in Aviemore you have the choice to do the northern or southern loop first. I’d probably cut up the Old Logging Way from Aviemore to Loch Morlich, then do the loop over Bynack Mor to Linn of Dee, then the Tilt section, then up the Gaick, back through Rothiemurchus round to Tomtintoul, Braemar, Geldie and Feshie. That gets the Lairig an Laoigh schlep out of the way early and you get to the Fords of Avon when you are still fresh.
It’s still covering the same distance, just in a slightly different order. finish back at Loch Morlich if you want to say you’ve been on all the route.
Ruigh Aitchechan (Feshie) is still under construction. It was supposed to have been completed last September but it’s been difficult to get any progress updates or a revised opening date. Bob Scotts and Ryvoan are the obvious other bothies. There’s also Inshriach/Drakes but I can’t see it would come at a great time in your ride. That red-roofed building at Ruigh nan Clach might be fine if you enjoy Carnmore. Personally, there’s only so much sheep-shit odour I can take.
Little snow this year means there’s unlikely to be any major meltwater run-off. In fact we’ve a prediction of 15/16C inland this weekend….
As for the Tilt options, heading straight down without doing the Fealar-Daldhu diversion would be the cop-out only a wimp would choose.
The full double-loop is just under 300km. The record currently stands at around 18 hours. 😯