I know this isn't a discussion about fistulas, but having worked in dialysis, I just wanted to clarify that under NO circumstances are fistula needles inserted bevel down. A long time ago, needles were inserted, bevel up, then "flipped" once inside the fistula. This is no longer accepted practice as it can A) shred the vein while flipping and if not flipped back to bevel up upon removal, would tear the hell out of peoples skin. I would asssume going in bevel down, it would do the same.
Having said that, I can't seem to think of a reason to insert bevel down. With all of the other options available-another IV site, no tourniquet, another person to do the sticking, etc. it just doesn't seem like this would be necessary and it isn't standard practice here.