I am in awe of anyone who does ultra running whether they have diabetes or not. Although as someone with diabetes who runs a few miles, I am well aware what extra challenges our condition throws at us.
Have you taken a look at Roddy Riddles escapades (
https://roddyriddle.com/). He is a pretty amazing chap and has taken his ultra running to what I thought is the most extreme with Marathon des Sable. His website seems to be a little out of date and mentions he is going to do the 6622 Ultra in 2016.