Thanks for the info , LL and Chris.
I agree about the findhorn area and the B9007 NE of Aviemore is one of my favorite roads, not that I get up there often enough. Yes sundays can be a problem. On an S4 I've managed about 90 miles on around half a tank at sensible cruising speeds based on refilling litres but have never chanced much longer without a stop just incase
Being in central scotland, I could probably do the whole loop in a one'r but to actually enjoy it needs an overnight or two.