I have the AEM e85 pump. I can run it pretty low because I've hacked out the bottom of the canister. I had 3 or 4 pumps that all failed since I went e85. The AEM has been in the longest. So much for those who say the stock pumps won't have an issue with e85.
Still, I try not to let the fuel get below 1/4. It's just good practice for several reasons. Plus, filling up with e85 is so "cheap" I almost look forward to topping it off.