I have a pair of the 83 degree stems and the dealer would not install them when I had a set of tires put on. He said they were not safe and could become undone causing a rapid deflation. Personally, I think he was full of owl dung. I had them put on the short rubber stems and do not find it all that difficult to check tire pressure with my 90 degree digital tire gauge.
If I should decide to use the 83 degree stems in the future, why not have the stems facing forward? Would that not eliminate any danger of something snagging them? How about less wind drag as well!!!