Well that went OK! As I left I set a 7hr temporary basal rate of 50%, which was roughly in the ballpark, and tested about every hour or so. Just before I left I downed a Mars recovery drink (40g) and used the bolus calculator for that. An hour later I was at 4.8, so necked a sports gel (20g) and a little electrolyte (15g) with no bolus, and that got me home at 6.9.
I guess I should have reduced the bolus for the Mars drink, but the diabetes centre said to leave the exercise adjustment % for the moment in the bolus calculator.
When the 7hr temp basal rate ended, I started another one at 70% for another seven hours, and woke up at 7.4. All this for around 5 hours of exercising at low intensity. Does this seem sort of reasonable to you?
Training - nothing special, just winter long slow distance maintenance really.