I don't do much erging these days (used to do a fair bit), but I do a good amount of running and cycling and have a good idea of the energy needs to each and to be honest they are pretty comparable. Duration and intensity are also key.
Today as an example, 30km/3hrs running at pretty near my max aerobic level, so burning a mix of both fats and carbs and I've ingested 325g carbs so far today.
Tuesday was a cycling club TT, high intensity and over in half an hour. TOtal carbs ingested 180g. I've actually seen my BG rise after a TT due to the shunt from the liver caused by the adrenaline.
Have you read the Diabetic Athletes Handbook, written by a diabetic doctor? A bit noddy in it's basic physiology, Noakes and others in Lore of Running are much better, but has some good sports specific stuff. I've also got a copy of Handbook of Exercise in Diabetes on order, by the ADA.
Personally here I don't think you can do enough research and also testing yourself frequently during your training. I'm testing every 30 mins or so at the moment to get a picture of how my levels vary and also afterwards.
You don't say what you are taking in during a session?