Title: Tubes don't show same diameter

Text from bug tracker:
When creating tubes with sharp angled curves, the diameter of tubes look weird.
I won't say it's a bug - it's just not expected. But I tested it with AoI 1.7.1 and 2.4.1 - the behavior stays the same. So it's persistant at least. Maybe it needs a radio button to control the behavior? (Then I need to put that under RFE, or not?)
http://freenet-homepage.de/vidiot/AOI/Tube_problems.jpg
Harald