Update: A friend let me borrow a vintage track bike, and - to my amazement - I have been riding it without mishap and with much enjoyment! It is a custom frame that was made for an Austrian bicycle racer, and it just happens to be in exactly my size. I will be staying in Vienna again this Fall and in Spring 2011, and will buy a seasonal velodrome license for the 2010/2011 season. If I practice all summer, I think I will be ready. Thank you for your support; I am so excited!