Coincidentally a mate and I binned a Cairngorms Loop attempt at the end of August at the Geldie - we stayed in the sumptuous cottage (a lot less grim than a bivi in the rain) and found the burn in spate the following morning so escaped out to
Feshiebridge.
I'd recommend the bothy about fifteen miles further on as a good stop after day 1.
I think the hardest bit of that route is turning right at the Geldie and continuing on. Having done both exactly what you did as well as managing to keep going on my second attempt I can entirely sympathise with your decision (it was sore butt and wrists that did for me!) and 95 miles in one day over that loop is a major achievement.
I tell you though I wish I'd waited a fortnight to do my second attempt as the trails and rivers look so dry compared to when I did it!